manwal  of 


plilitavtr  Sxslti  (Bn^inzsving 


REESE   LIBRARY  ; 

OF  THE  .  ;^ 

UNIVERSITY  OF  CALIFORNIA.    [ 
Received  •       ^4<ly>x.  ^  .  ]8oS^ 

zAccesswns  No.SS'S^l^  .      Class  No. 


^^'•:^ 


MANUAL 


Military  Field  Engineering 


FOR    TIIK    USE    OF 


OFFICERS  AND  TROOPS  OF  THE  LINE. 


PREPARED    AT    THE 


UNITED  STATES  INFANTRY  AND  CAVALRY  SCHOOL 

BY  THE 

Department  of  Engineering, 

Capt.  Wm.  D.  Beach,  3RD  Cavalry,  Instructor. 


Fort  Leavenworth,  Kansas, 
July,  1894. 


■q  -  ^  o 


Entered  according  to  Act  of  Congress  in  the  year  1894,  by  VVm.  D.  Beach, 
IN  THE  Office  of  the  Librarian  of  Congress,  at  Washington. 


Press  of  Lawton  &  Burnap,  Kansas  City,  Mo. 


PREFACE. 

The  necessity  existing  at  the  Infantry  and  Cavalry  School  for  a 
text  book  on  Field  Engineering,  including  the  various  military 
expedients  recognized  in  our  service,  is  deemed  sufficient  reason 
for  the  following  pages. 

Most  of  the  subjects  treated  of  in  this  volume  may  be  found  in 
various  military  works  published  in  our  country  during  the  past 
twenty-five  years,  but  the  fact  remains  that  no  one  book  has  cov- 
ered the  required  ground,  nor  has  their  revision  been  of  very  re- 
cent date;  while,  at  the  same  time,  the  new  field  gun  and  small 
calibre  rifle  have  necessarilir  modified  previously  existing  profiles 
of  Field  Works  and  Shelter  Trenches. 

Access  has  been  had  to  corresponding  publications  of  the  Ger- 
mans, French,  English  and  Austrians,  as  well  as  to  our  own  Offi- 
cial Rebellion  Records  and  many  other  available  sources,  native 
and  foreign. 

It  has  been  the  endeavor  to  limit  the  scope  of  this  work  to  sub- 
jects considered  indispensable  as  a  part  of  a  line  officer's  edu- 
cation. 

The  following  Assistant  Instructors  in  the  Department  of  En- 
gineering, viz  : — 1st  Lieut.  E.  A.  Root,  19th  Infantry;  1st  Lieut. 
W.  C.  Wren,  17th  Infantry  and  1st  Lieut.  T.  H.  Slavens,  6th  Cav- 
alry have  been  associated  with  the  undersigned  in  the  prepara- 
tion of  this  volume. 

Wm.  D.  Beach, 

Captain,  3rd  Cavalry. 
U.  S.  Infantry  and  Cavalry  School, 

Fort  Leavenworth,  Kansas,  July,  1894. 


List  of  Books  Consulted  in  the  Preparation  of  this  Work 


Aide  Memoire,  R.  E Vols.  1-2. 

A  Move  for  Better  Roads L.  A.  Haupf. 

Appleton's  Cyclopaedia  of  Applied  Mechanics Fo/s.  /  V. 

Civil  Engineering WJieeler. 

Cours  de  Fortification  Passagere De  Guise. 

Ecole  de  Fortification  de  Campagne French. 

Elements  of  Field  Fortification Wheeler. 

Engineering  News  Magazine. 

Engineer's  Pocket-Book Trautwine. 

Field  Fortification Tamer. 

Field  Fortification .Hutchinson.. 

Field  Works Brackenhia-fj. 

Field  Works  used   in  War.      (Translation 

from  the  German) Wilson. 

Good  Roads Magazine. 

Gunpowder  and  high  Explosives  Walke. 

International  Cyclopaedia Dodd,  Mead  <i-  ( v>. 

Journal  of  the  Military  Service  Institvition 

of  the  U.  S. 
Journal  of  the  U.  S.  Cavalry  Association. 

Manual  for  Engineer  Troops Duane. 

Manual  of  Military  Engineering Ernst. 

Manual  for  Railway  Engineers G.  L.  Vose. 

Manuel  de  Fortification  de  Campagne. . . .  BriaJuiont. 
Manuel   des  Travaux   de    Fortification   de 

Campagne  par  un  Capitaine  d'  Infanterie. 

Manuel  de  Fortification Plessix  and  Legrand. 

Manual  of  Heavy  Artillery Tidball. 

Military  Bridges Haupt. 

Military  Bridges Chester. 

Military  Engineering.     Instruction  in Chatham  Course. 

Military  Transport Furse. 

Modern  High  Explosives Eissler. 

Notes  on  Military  Hygiene   A.  A.  Woodhull. 

Official  Records  of  the  Rebellion.     U.  S War  Department. 

Organization  and  Tactics Wagner. 

Pionier  Taschenbuch,  Berlin,  1893. Official. 

Report  of  Chief  Signal  Officer.     U.  S.  1893. TFar  De/xtrf nienf. 

Roads  and  Railroads Chester, 

Roads  and  Railroads Gillespie. 

Roads,  Streets,  and  Pavements Gilhnore. 

Temporary  Fortification Chester. 

The  American  Railway ' Scrihncf. 

U.  S.  Bridge  Equipage  and  Drill Wat-  Dcinirl inent. 


"rAB^/K   OK   CONTE^NO^S. 


Chapter. 

Page. 

Plate. 

I 

General  Principles .               .    . 

7 

11 
14 

23 
31 
37 

II 

Fire,  Projectiles,  and  Penetra- 
tion   

III 

Field  Geometry 

,V- 

IV 

Hasty  Intrenchments,  Gun  Pits 
and  Epaulements 

3,  4 

V 

Clearing  the  Ground 

5,  6 

VI 

Obstacles 

7,  8 

VII 

VIII 

IX 

X 

XI 

XII 

XIII 

XIV 

XV 

XVI 

XVII 

XVIII 

XIX 

XX 

XXI 


Field  Works 

Working  Parties 

Revetting  Materials  and  Revet- 
ments   

Field  Casemates  and  Magazines 

Field  Works  in  Combination.  . 

Siege  Works 

Defense  of  Localities 

Use  of  Cordage  and  Spars 

Spar  Bridges 

Floating  Bridges 

Roads  

Railroads 

Telegraph  and  Telephone  Lines 

Demolitions •. . . 

Camping  Expedients 


45 
71 

74 
89 
95 
103 
109 
131 
149 
176 
212 
221 
235 
240 
257 


9-15 
16 

17,18 
19,  20 

21 
22,23 
24-29 
30-33 
34-40  a 
41-49 
50 
51-53 

54 
55-57 
58  60 


CNIVEBSITY 


NIANTJAL 


MILITARY  FIELD  ENGINEERING. 


CTTAPTF.Tl  T.-  Goiioral  Priiicii)les. 


1. — Military  Field  Engineering  may  be  defined  to  be  the 
art  of  utilizing  the  materials  at  hand  for  the  attainment  of  the 
security,  effectiveness,  health  and  comfort  of  an  army  in  the  field. 

The  modern  rifle  has  vastly  increased  'the  value  of  cover  both 
in  attack  and  defense,  and  rendered  necessary  the  application  of 
the  principles  of  fortification  to  an  army  in  the  field.  The  result 
to  be  obtained  in  all  fortification  is  to  so  strengthen  a  position,  by 
artificial  means,  that  a  force  may  successfully  resist  or  subdue 
another. 

2. — Fortification  is  divided  into  two  general  classes,  viz.; 

(a) — Permanent. 

{h) — Temporary  or  Field  Fortifications. 

With  the  former  this  manual  has  nothing  to  do. 

3. — The  latter  division  includes  three  quite  distinct  classes. 

The  first  comprises  all  works  devised  for  the  temporary  protec- 
tion of  important  points  such  as  cities,  arsenals,  bridges,  fords, 
positions,  etc.,  and  are  technically  known  as  Field  WorJcs. 


8  General  Principles. 

The  second  comprises  the  various  devices  of  the  engineer  for 
reducing  a  fortified  place  by  means  of  parallels  and  approaches, 
called  Siege  Works. 

The  third  division  relates  particularly  to  the  quickly  made  de- 
fenses by  which  an  army  in  the  presence  of  an  enemy  protects 
itself ;  these  are  known  as  Battle  Intrenchments  or  Hasty  In- 
trenehments, 

4. — A  Defensive  Position  is  one  affording  protection  from 
the  shot  and  observation  of  an  enemy  and,  at  the  same  time,  com- 
manding the  ground  in  front,  within  range. 

A  position  of  perfect  defense  is  not  possible,  but  the  following 
general  principles  are  to  be  fulfilled  as  nearly  as  circumstances 
will  permit. 

(1)  The  defenders'  position  should  conform  to  the  special  tacti- 
cal requirements  of  the  occasion*  and  should  be  such  as  to  favor 
the  use  of  their  relatively  strongest  arm. 

(2)  It  should  be  made  impossible  for  the  enemy  to  obtain  nat- 
ural cover  during  his  advance.  In  other  words,  the  position 
should  have  a  free  field  of  fire. 

(3)  The  defenders  should  be  protected  from  the  fire  and  view  of 
the  enemy  by  cover  so  arranged  as  not  to  interfere  with  counter 
attacks. 

(4)  The  advance  of  the  enemy  should  be  hindered  by  obstacles 
so  arranged  that  he  may  be  checked  while-  under  the  fire  of  the 
defenders. 

(5)  Communications  should  be  such  that  the  defenders  may 
freely  move  from  one  part  of  the  position  to  another,  while  the 
contrary  should  obtain  with  respect  to  the  enemy's  ground  in 
front. 

The  chief  requisite  of  a  defensive  position  is  a  free  field  of  fire, 
especially  at  short  and  mid  ranges.  If  the  position  is  judiciously 
selected  the  field  of  fire  will  generally  be  obtained  without  much 
difficulty,  but  the  advantages  of  the  position  and  the  effect  of  the 
fire  may  be  enhanced  by  temporary  fortifications.  The  cutting 
down  of  slight  ridges  which  might  afford  cover  for  the  enemy 
within  effective  range  or  the  removal  of  hedges,  fences,  etc.,  may 

*A  purely  defensive  position,  for  instance,  might  have  its  flanks  resting  on  impassable 
obstacles,  and  thus  be  secure  from  a  turning  movement,  but  this  same  position  might  be 
found  to  be  a  faulty  one  were  a  quick  ottensive  movement,  by  the  defenders,  contem- 
plated. 


General  Principles.  9 

sometimes  be  of  more  benefit  than  the  actual  preparation  of  de- 
fenses. 

In  the  present  advanced  state  of  efficiency  of  fire-arms,  artificial 
cover  is,  however,  of  greater  importance  than  ever  before.  Con- 
structed in  the  right  place,  at  the  proper  time,  field  fortifications 
may  render  indispensable  service,  while  their  neglect  may  insure 
defeat. 

5. — While  formerly  it  was  the  special  province  of  the  Engineer 
to  lay  out  and  supervise  the  construction  of  defensive  works,  it 
has  now,  under  the  changed  condition  of  warfare,  become  the 
work  of  the  Line  as  well,  and  it  may  be  laid  down  as  an  accepted 
rule  that  the  defensive  arrangements  for  a  given  position  are  to 
be  made  by  the  troops  which  are  to  occupy  it. 

These  changes  have  affected  the  art  in  many  ways.  The  field 
works  now  constructed  are  simpler,  ruder,  less  regular,  and  less 
angular  than  before.  An  army  in  presence  of  an  enemy  always 
fortifies,  whether  in  camp,  in  bivouac,  or  in  line. 

6. — Rapidity  of  execution  renders  necessary  the  adoption  of 
fixed  types  of  works  in  the  exercises  in  time  of  peace ;  but  these 
types  will  sometimes  be  susceptible  of  modification  in  their  real 
application.  However,  even  in  war,  the  endeavor  should  be  to 
approximate  to  the  regulation  forms,  for  they  are  deduced  from 
experience  and  observation,  and  realize,  as  well  as  possible,  for 
each  particular  case,  the  best  conditions  of  resistance  compatible 
with  rapidity  of  execution. 

The  advantage  of  regulation  types  is  understood  at  once  when 
it  is  borne  in  mind  that,  upon  the  battle-field,  there  should  be  no 
hesitation ;  everyone  should  stick  to  his  individual  role  in  order 
to  unite  efficiently  in  combined  action. 

Thorough  study  and  frequent  practical  exercises,  conducted 
methodically,  are  indispensable  in  order  to  escape  feeling  one's 
way,  with  the  loss  of  time  that  an  insufficient  instruction  renders 
inevitable.  Upon  the  battle-field  a  few  minutes  may  decide  the 
fate  of  armies  in  each  other's  sight. 

T. — Fortification,  which  at  first  glance  may  appear  to  dominate, 
as  representing  the  "security"  and  "effectiveness"  of  an  army, 
the  other  and  apparently  less  important  subjects  relating  to 
health  and  comfort,  is,  however,  so  intimately  connected  with 
them  that  neglect  of  one  may  render  all  the  others  useless. 
Thus,   "bridges,"  "roads,"  and  "railroads"  may,  under  certain 


10  General  Principles. 

conditions,  relate  particularly  to  the  effectiveness  and  security  of 
an  army,  in  connection  with  Fortification,  while  under  other  cir- 
cumstances they  may  be  as  important  as  various  "camping  expe- 
dients" in  the  attainment  of  "health"  and  "comfort." 


CHAPTKK  II.     Fire,  Projectiles  and  Penetration. 


8. — Fire  as  regards  its  direction  is  classified  as  follows: 

(1)  Frontal,  when  it  is  delivered  at  right  angles  to  the  front 
of  the  enemy's  line,  and  sometimes  so  termed  when  delivered 
straight  to  its  own  front. 

(2)  Oblique,  when  the  direction  of  the  fire  is  at  an  oblique 
angle  to  the  front  of  the  enemy's  line. 

(3)  Enfilade,  which  is  delivered  from  positions  on  the  prolon- 
gation of  the  enemy's  line.  In  this  case,  the  line  of  fire  sweeps 
the  enemy's  front.  When  fire  is  used  to  sweep  along  the  front 
of  a  defensive  line  and  thus  enfilade  the  assailants  as  they  ap- 
proach the  position,  it  is  known  as  flanking  fire. 

(4)  Reverse,  when  delivered  so  as  to  strike  troops  or  lines  of 
defense  from  the  rear. 

(5)  Cross,  when  the  lines  of  fire  from  different  positions  cross 
on  or  in  front  of  the  enemy's  line. 

As  regards  its  trajectory  it  is  classified  as 

(1)  Direct,  when  delivered  at  seen  objects  at  moderate  angles 
of  elevation — in  the  case  of  artillery  when  delivered  at  seen  ob- 
jects, with  service  charges  at  elevations  not  exceeding  15° 

(2)  Indirect  or  Curved,  when  delivered  with  small  arms 
against  an  unseen  object  protected  by  a  seen  covering  obstacle — 
in  the  case  of  artillery,  as  above,  or,  with  guns,  howitzers  or  mor- 
tars with  reduced  charges  at  angles  not  exceeding  15°.  Thus 
firing  over  an  intervening  hill  at  troops  sheltered  behind  it  would 
be  an  example  of  indirect  fire. 

(3)  Iligli  Angle,  when  used  at  angles  exceeding  15°. 

(4)  Grazing,  when  the  projectile  travels  approximately  paral- 
lel to  the  ground. 

9. — Tlie  Artillery  Projectiles  used  in  the  U.  S.  Army  are 
shell,  shrapnel  and  canister. 


12  FiKE,  Projectiles  and  Penetration. 

81iell.  Shell  may  be  classified  as  common  shell  and  torpedo 
shell.  The  common  shell  is  "a  hollow  cast-iron  or  steel  cylinder 
with  an  ogival  head  closed  at  one  end  and  filled  with  powder." 
The  torpedo  shell  is  filled  with  gun-cotton,  or  other  high  explo- 
sive. Either  shell  may  be  characterized  as  a  flying  mine,  the 
chief  object  of  which  is  to  destroy  material  objects  at  a  distance, 
though  the  common  shell  may  also  be  effectively  used  against 
troops. 

lO. — 81irax)iiel  differs  from  common  shell  in  being  filled  with 
bullets,  and  having  only  a  sufficient  bursting  charge  to  rupture 
the  envelope  and  release  the  bullets,  which  then  move  with  a 
velocity  which  the  projectile  had  at  the  moment  of  bursting.  The 
bullets  are  assembled  in  circular  layers  and  held  in  position  by 
"separators,"  which  are  short  cast-iron  cylinders  with  hemispher- 
ical cavities  into  which  the  bullets  fit.  The  shrapnel  for  the  3.2 
inch  gun  contain  162  bullets  }^  in.  in  diameter,  and  weighing  11 
to  the  lb.  The  total  number  of  bullets  and  individual  pieces  in 
the  shrapnel  is  201. 

11. — Canister,  which  is  practically  obsolete,  is  made  of  sheet- 
iron  or  tin  in  the  shape  of  an  ordinary  can,  and  is  filled  with  bul- 
lets held  in  place  by  filling  the  interstices  between  the  bullets 
with  saw-dust,  sulphur  or  rosin;  the  can  is  ruptured  and  its  con- 
tents dispersed  by  the  discharge  of  the  piece. 

12. — The  charges  in  the  shell  and  shrapnel  are  exploded  by 
means  of  a  combination  fuse;  by  combination  fuze  is  meant  one 
that  may  be  arranged  to  explode  the  charge  either  on  impact,  by 
percussion,  or  at  a  given  time  by  certain  arrangement  of  the  parts 
of  the  fuse. 

13.— Field  Guns  range  up  to  6000  yds.  but  will  be  seldom 
used  at  a  range  greater  than  2500  yds. 

14. — Tlie  17.  8.  Magazine  Rifle,  when  used  as  a  single 
loader,  has  fired  21  aimed  shots  in  one  minute,  and  when  used  as 
a  magazine  rifle,  23  shots  in  one  minute;  its  range  is  over  3000 
yds.  and  it  is  sighted  to  1900  yds. 

The  average  heights  over  which  fire  may  be  delivered,  are  as 
follows:  Man  standing  i  ft.  1  in.;  kneeling  3  ft;  lying  down  1  ft.; 
field  guns  3  ft. 

15.— The  following  thickness  of  material  may  be  considered  as 
proof  against  small  arm  projectiles  at  all  ranges: 


Fire,  Projectiles  and  Penetration.  13 

Sand 30  in. 

Boggy  or  turfy  ground 60  in. 

Gabion  filled  with  earth r 1 

Sand  bag  well  packed,  header 1 

"       "        "  "         stretcher 2 

Packed  snow 6  ft. 

Soft  wood 40  in. 

Oak  or  other  hard  wood 24  in. 

Grain  sheaves  piled 16  ft. 

Iron  plate /e  i^i- 

Steel  plate f  in. 

Masonry 20  in. 

Against  field  artillery. 

Earth 10  to  13  ft. 

Snow  well  packed 27  ft. 

Masonry  (for  a  short  time) 40  in. 


ClIAPTKH  IlI.-^Fielcl  GeoinetiT. 


16. — Before  proceeding  to  that  portion  of  field  engineering  which 
involves  geometry  some  of  its  simplest  applications  will  be 
explained. 

17. — Slopes.  The  usual  description  of  a  slope  is  by  a  fraction, 
the  numerator  being  the  height  and  the  denominator  the  base. 
Thus,  in  PI.  1,  Fig.  1,  the  vertical  height  is  l-6th  part  of  the  base, 
and  the  slope  is  read  as  1  on  6.    In  Pig.  2.,  the  slope  is  6  on  1. 

18.  -To  lay  out  a  Riglit  Angle:— First  Metliod.  Let 
A  be  a  point  in  the  line  BC,  Fig.  3.  Lay  off  from  A  the  equal 
distances  AD  and  AE.  With  a  radius  greater  than  AD,  and  with 
D  and  E  as  centers,  describe  arcs  cutting  each  other  at  X.  Join 
X  with  A.    Then  is  XA  perpendicular  to  BC. 

Second  Metliod.  Find  a  point  such  that  the  distances  are 
in  the  proportions  of  3,  4  and  5:  then  will  the  angle  included  be- 
tween the  two  shorter  sides  be  a  right  angle.  Thus  (Fig.  4.)  with 
chain  or  tape  measure  the  distance  AD  equal  to  4  yds.  Place  one 
end  of  tape  at  D,  the  other  at  A,  pulling  it  out  and  making 
XD  equal  to  5  yards,  XA  equal  to  3  yards. 

Tliird  Metliod.  At  extremity  of  line,  as  A  (Fig.  4.),  assume 
any  point  as  C.  Measure  distance  CA,  set  a  stake  on  line  BA  at 
a  distance  from  C  equal  to  CA,  as  D.  Set  a  third  stake  on  line 
CD  at  X  making  CX  equal  to  CD.  Then  will  XA  be  perpendicu- 
lar to  BA. 

19.— To  erect  a  i)eri>endiciilar  to  a  line  Croni  a  i)oiiit 
Avitlioiit.  Let  X  (Fig.  5)  be  the  point  without,  then,  with  X  as 
a  center,  and  a  distance  greater  than  XA  as  radius,  describe  an 
arc  cutting  BC  at  D  and  E.  With  D  and  E  as  centers,  and  with 
a  radius  greater  than  DA,  describe  arcs  cutting  each  other  at  Y. 
Join  X  and  Y.    Then  will  XY  be  perpendicular  to  BC. 

20.     To  bisect  a  given  angle.     Let  ABC  (Fi-.  (S.j  Ix    the 


PLATE  1. 


Figure  1. 


Figure  2. 


--x^^RNIA.  .   Figure  8 


Figure  3. 


B     '.D 
Figure  4 


E    c 

X 


Fig^ure  9. 


A        C      ' 


'      D      '    B 


Figure  5 


^^^-^-.---''A  Figure  10 


B       D" 


E     C 


B       D    C 


Figure  11 


Y 


Field  Geometry.  17 

angle.  With  A  as  a  center,  and  with  any  convenient  radius,  as 
AD,  describe  an  arc  cutting  AB  and  AC  at  E  and  D.  With  D  and 
E  as  centers,  describe  arcs  cutting  each  other  at  X.  Join  X  with 
A.    The  line  XA  bisects  the  angle  ABC. 

21. — To  lay  out  an  equilateral  triangle  constructing 
adjacent  angles  of  GO°  and  120°.  Let  AB  (Fig.  7)  be  a 
given  line.  Lay  off  from  B  any  convenient  distance,  as  BE.  Then, 
with  B  and  E  as  centers,  and  a  radius  equal  to  BE,  describe  arcs 
cutting  each  other  at  D.  Join  D  with  E  and  B.  The  angles  DEB, 
DBE  and  EDB,  are  each  equal  to  60°.  The  angle  AED  is  equal 
to  120°.  Combining  this  method  with  that  of  slopes  an  angle  of 
almost  any  number  of  degrees  can  be  laid  out. 

22. — To  lay  out  an  angle  equal  to  a  given  angle.  Let 
X  (Fig.  8)  be  a  point  in  the  line  AB,  from  which  it  is  required  to 
lay  out  an  angle  equal  to  OEC.  Fix  the  points  O  and  C  at  con- 
venient distances  from  E.  From  X  lay  off  XG  equal  to  OE. 
Then,  with  X  and  G  as  centers,  and  EC  and  OC  as  radii  respec- 
tively, strike  arcs  intersecting  at  F.  Join  X  and  F.  The  angle 
FXG  is  equal  to  the  angle  CEO. 

23. — To  draAv  a  line  parallel  to  a  given  line  and  at  a 
given  distance  from  it.  Let  AB  (Fig.  9)  be  the  given  line. 
From  any  two  points,  as  C  and  D,  erect  perpendiculars.  On  these 
lay  off  the  required  distance  CE  and  DF.    Join  E  and  F. 

24. — To  And  tlie  distance  between  any  two  points 

Av  lien  it  cannot  be  measured  directly.     First  Metliod. 

To  hnd  AO,  take  a  point  B  in  line  with  AO  and  from  this  point 

(Fig.  10)  lay  off  any  convenient  angle,  as  ABC.    At  D  make  EDC 

equal  to  ABC.    Measure  BC,  DC  and  DE,  putting  E  in  the  line 

CO.    From  similar  triangles 

BO  :  BC  ::  DE  :  DC  .-.  BO  =:  ?^J<^E 

DC 

From  the  result  thus  found,  substract  the  distance  AB.  The 
remainder  is  the  distance  AO. 

Second  Metliod.  (Fig.  11.)  Mark  B  in  prolongation  of  the 
line  AO.  Assume  any  point  as  C.  Lay  off  AF,  making  AC 
equal  to  CF:  also  BE,  making  BC  equal  to  CE.  Prolong  EF 
until  a  point  K  is  found  in  line  with  CO.  Measure  FK.  This  is 
the  required  distance. 

25.  —Areas.  To  lind  tlie  area  of  a  rectangle.  Multiply 
the  base  by  the  height. 


18  Field  Geometry. 

To  find  tlie  area  of  a  trai>ezoid.  Multiply  the  sum  of 
the  two  parallel  sides  by  the  perpendicular  distance  between  them 
and  take  half  the  product. 

To  find  tlie  area  of  a  triaii<>le.  Multiply  the  base  by  the 
altitude  and  take  half  the  product.     Or, 


Area  =  \)  s  (s-a)   (s-b)   (s-c) 
in  which  s  is  the  half  sum  of  the  three  sides  a,  b,  and  c.     Or, 

Area  =  J  a  b  sin  C 
in  which  a  and  b  are  two  sides  and  c  the  included  angle. 

26.— Tlie  Field  T^evel  (PI.  2,  Fig.  1)  consists  of  three 
strips  of  w^ood  A,  B  and  O,  each  Y^  in.  thick  and  2  in.  w4de.  A 
being  62  in.  long,  B  and  C  each  44.42  in.  The  distance  between 
centres  on  A  is  60  in.  on  B  and  C  42.42  in.  This  makes  a  right 
angle  between  B  and  C.  There  is  a  thumb  nut  at  E  clamping 
the  arm  B  to  the  arm  A  when  the  level  is  used.  The  screw  at 
F  projects,  holding  the  arm  B,  when  folded,  up.  There  is  a  stud 
at  H,  affording  an  attachment  for  a  plumb  bob.  There  are  per- 
manent joints  between  B  and  C,  and  A  and  C. 

Fig.  1  shows  the  level  and  its  joints,  plumb  bob  for  reading 
slopes,  and  spirit  level.      Fig.  2  shows  side  for  protracting  angles. 

27. — Uses  of  Tjevel.     The  level  may  be  used  as  follows: 

(1)  As  a  spirit-level,  the  level  being  on  the  edge  C 

(2)  As  a  square  for  setting  out  a  right  rngle. 

(3)  As  a  protractor. 

(4)  For  setting  off  slopes. 

(5)  As  a  mason's  level  with  a  plumb  bob. 


."PLATE  2. 


^-^^■^■■cM 


PLATE  3. 


^CNIVEEfelTY 


CHAPTER  IT.— Hasty  Iiitieiiclimeiits,  Gun  Pits  and 
Epaiilements. 


28. — The  intensity  of  fire  made  possible  by  the  fire-arms  of  to- 
day renders  some  form  of  shelter  on  the  field  of  battle  imperative. 
Circumstances  may  occur  when  advancing  lines  of  skirmishers 
will  find  natural  shelter,  but  in  most  cases  artificial  cover  must 
be  constructed  on  the  spot.  The  fortifications  used  on  the  field 
of  battle  depend,  as  to  their  position,  extent,  and  use,  on  the 
ground  and  on  the  tactical  advantages  to  be  gained,  and,  in 
conformity  to  this  idea,  they  are  constructed  at  the  time  of  the 
battle  and  not  before.  They  are  called  "Battle'*  or  "Hasty"  in- 
trenchments  and  consist  of  cover  for 

(1)  Skirmishers  lying,  kneeling,  or  sitting. 

(2)  Firing  line.  Supports  and  Reserves  kneeling,  sitting,  or 
standing. 

(3)  Gun  pits  and  Epaulements. 

29. — PI.  3,  Fig.  1,  shows  the  section  of  shelter  trench  for  skir- 
mishers— lying  down.  It  gives  earth  protection  to  the  depth  of 
30  inches,  which  will  stop  small  arms  projectiles,  except  when 
'struck  in  the  most  favorable  spot  for  penetration.  The  time  with 
one  large  spade  and  one  pick — one  man — about  15  minutes ;  with, 
small  spade,  about  20  to  25  minutes. 

30. — ^For  men  kneeling  or  sitting  in  two  ranks,  cover  is  gained 
by  deepening  the  trench  already  dug  to  20  ins.  and  making  it 
5  ft.  wide,  thus  obtaining  a  trench  having  a  defense  of  1  ft.  4  in. 
high  and  about  58  in.  thick.  Time  about  30  minutes — small 
spade. ^  If  single  rank  is  used  the  trench  need  only  be  2  ft.  6  in. 
wide.     (Fig.  2.) 

31. — Cover  standing  is  obtained  by  deepening  the  kneeling 
trench  to  48  in.,  leaving  a  step  20  in.  high  and  3  ft.  wide  next  the 
front  wall  of  trench  so  as  to  facilitate  the  leaving  of  the  trenches 

3 


24:       Hasty  Intrenchments,  Gun  Pits  and  Epaulements. 

to  the  front  and  also  to  serve  as  a  banquette  for  men  firing  over 
defense.  The  earth  defense  should  thus  be  60  in.  thick  and  2  ft. 
high;  time — infantry  spade — 1%  to  3  hours.  Whenever  it  is  pos- 
sible the  interior  slope  should  be  as  near  vertical  as  possible. 
(Fig.  3.) 

32. — When  isolated  trenches  or  rifle  pits  are  desired  for  the  use 
of  riflemen  they  should  be  made  with  the  same  section  as  the  , 
trenches  for  cover  standing,  2  paces  being  taken  as  the  length  of 
trench  for  each  man.  Should  a  more  thorough  shelter  be  desired 
than  is  given  by  the  cover  standing  the  earth  defense  may  be  in- 
creased by  digging  a  ditch  in  front,  care  being  taken  that  it  is  so 
far  to  the  •  front  that  sufficient  distance  is  given  to  develop  the 
existing  works  into  the  normal  field  works — i.  e.,  15  to  18  feet. 

33. — The  trenches  here  illustrated  are  all  made  on  level  ground 
and  are  simply  types  showing  the  best  form  and  giving  general 
ideas  as  to  the  time  required  to  construct  cover.  They  must  be 
varied  according  to  the  kind  of  earth  in  which  they  are  to  be 
made  and  such  modifications  introduced  as  will  strengthen  the 
cover  without  increasing  the  time  used.  The  location  of  trenches 
depends  primarily  on  tactical  considerations,  secondarily  on  the 
nature  of  the  ground.  Sand  or  stony  ground  should,  if  possible, 
be  avoided  in  selecting  the  position  of  trenches.  The  eye  should 
be  placed  a  distance  above  the  ground  equal  to  the  height  of  the 
completed  parapet  in  order  to  locate  the  trench  so  as  to  obtain  a 
clear  field  of  fire  to  the  front.  Shelter  trenches  should  always 
occupy  a  position  giving  the  greatest  development  of  fire  to  the 
front  and  are  generally  constructed  at  the  crest  of  the  most 
abrupt  slope. 

34.— In  all  trenches,  except  those  for  skirmishers  lying  down, 
intervals  in  the  line  should  be  left  for  the  passage  to  the  front  of 
Artillery  and  Cavalry  — this  is  especially  necessary  when  the 
cover  standing  is  used.  These  intervals  will  vary  in  width  accord- 
ing to  circumstances  but  should  never  be  so  wide  as  to  preclude 
their  defense  by  the  trenches  adjoining  the  opening.  When 
stones  are  encountered  in  digging  they  should  be  imbedded  in 
the  parapet  and  well  covered  with  earth,  as  they  splinter  badly 
when  struck  by  bullets  or  shrapnel  fragments. 

35._Wrhen  men  are  required  to  remain  in  the  trenches  for  any 
considerable  period  they  should  be  provided  with  splinter  proofs 
or  shelters  of  some  kind.     Planks,  old  lumber,  doors,  etc.,  may  be 


Hasty  Intrenchments,  Gun  Pits  and  Epaulements.      25 

used,  in  absence  of  which  small  poles  are  available ;  they  should 
be  laid  with  one  end  on  the  parapet  and  the  other  resting  on  the 
earth  in  rear  of  the  trench  and  then  covered  with  2  to  3  inches  of 
earth.  This  defense,  while  not  proof  against  bursting  shells,  will 
protect  the  men  from  dropping  bullets  and  shrapnel  fragments. 
(Fig.  4.) 

36. — Ijooi^  Holes  may  be  provided  by  placing  head  logs  half 
imbedded  in  the  parapet  or  resting  on  sandbags  on  the  crest  and 
leaving  spaces  beneath  for  the  rifle,  or  with  sandbags,  two  being 
laid  lengthways  to  form  the  sides  and  two  resting  on  top,  as 
shown  in  Figs.  6,  7,  8,  9,  10.  Brushwood  may  be  used  by  laying 
it  on  top  of  the  excavated  loop  hole  and  covering  it  over  with 
earth ;  all  loop  holes  for  musketry  splay  inwards. 

The  best  practice  is  not  to  use  head  logs  or  construct  loop  holes 
(unless  the  force  is  acting  solely  on  the  defensive),  as  their  use 
impels  men  to  hesitate  to  leave  their  cover  when  the  advance  is 
ordered. 

37. — When  necessary  to  intrench  supports  or  reserves,  the  cover 
kneeling  or  standing  should  be  used  in  parallel  rows  and  close  to 
one  another.    Fig.  5. 

38.— The  advantages  of  the  shelters  for  men  lying  and  kneel- 
ing are, 

(1)  That  they  present  but  small  difficulties  to  the  advance  of 
Cavalry  or  A;*tillery  over  and  through  them. 

(2)  They  offer  but  a  small-  target  to  artillery  fire. 

(3)  They  are  not  often  penetrated  by  rifle  bullets. 

(4)  They  are  easily  surmounted  by  their  defenders  when  tak- 
ing the  offensive. 

Their  disadvantages  are,  ^ 

(1)  That,  being  of  low  mliej^  they  often  have  their  field  of  fire 
limited  by  small  folds  of  the  ground,  although  this  may  be  elim- 
inated to  a  large  extent  by  care  in  selecting  the  site. 

(2)  In  wet  weather  they  become  muddy  and  uncomfortable. 
In  all  intrenchments  it  is  well  to  loosen  the  earth  in  front,  to  les- 
sen the  effect  of  shells  striking  them.  It  is  also  necessary  to  dis- 
guise the  intrenchment  by  branches,  sods,  etc.,  so  as  to  deceive 
the  enemy  in  regard  to  their  location. 

39.^ — Cover  for  guns  and  caissons  is  obtained  in  either  of  two 
ways :— 


26      Hasty  Intrenchments,  Gun  Pits  and  Epaulements. 

(1)  By  sinking  the  guns  below  the  surface  of  the  ground  and 
building  a  parapet  with  the  excavated  earth.    Called  Gun  Pits. 

(2)  By  building  an  epaulement  in  front  of  and  around  the  gun, 
the  gun  in  this  case  resting  on  the  natural  surface  of  the  ground. 
Called  Gun  Epaulements. 

The  Gun  Epaulements  shown  (PI.  4,  Fig.  5)  may  be  constructed 
while  the  gun  is  in  action,  which  cannot  be  done  with  any  form 
of  pit,  as  pits  must  be  completed  before  the  gun  can  be  put  into 
action.  Gun  pits  of  various  kinds  are  shown  in  Figs.  1,  2,  3  and 
4.*  When  the  ground  is  soft,  or  in  plowed  fields,  the  pit  is  the 
better  construction  for  use. 

40. — In  constructing  any  earthworks  plows  may  be  used  to  ad- 
vantage to  loosen  up  the  earth.  The  furrows  should  begin  at  the 
back  line  of  the  trench  and  then  return  along  the  front  line  until 
the  earth  is  loosened  in  all  the  trenches ;  two  or  three  plows  fol- 
lowing each  other  at  intervals  can  be  used  with  advantage. 

*  Figrs.  1,  2  and  4,  VI.  4,  are  from  U.  S.  Artillery  Drill  Regulations. 


PIATE  4. 


FIGURE  5. 


j       »3  6  Ij     (N   +3'        n-t-s'e"       f 


*3'6"' 


««wa  _  5' Jjiw\»y/<«»«W/'/W!{ 


PLATE  5.. 


CHAPTER  v.— Clearing:  tlie  Ground. 


41. — The  tools  more  especially  used  in  the  field  may  be  divided 
into  two  classes. 

(1)  Iiitrencliiiig  tools,  such  as  the  pick,  the  shovel  (long 
and  short  handled),  the  spade,  the  picket  shovel,  and  the  hunting 
knife  (Infantry  equipment.) 

(2)  Cutting  tools,  such  as  the  ax,  the  hand  ax,  the  log  saw, 
the  hand  saw,  the  linked  felling  saw,  the  gabion  knife  (pruning 
knife),  the  hunting  knife,  the  bush  hook  and  the  wire  cutter. 
(PL  5  and  6.) 

42. — The  choice  of  a  defensive  position  in  which  the  foreground 
is  free  from  obstructions  and  favorable  to  the  defenders'  fire  is  of 
the  utmost  importance:  more  or  less  clearing,  however,  will 
usually  be  necessary.  Clearing  must  be  systematically  done  and, 
as  in  all  other  work,  should  be  undertaken  by  complete  organiza- 
tions or  parts  of  organizations,  under  their  own  officers. 

43. — The  extent  (theoretical)  to  which  the  foreground  should  be 
cleared  is  equal  to  the  effective  range  of  the  defenders'  weapons. 
Practically,  as  wide  a  space  within  this  limit,  is  to  be  cleared,  as 
is  consistent  with  the  time  and  labor  available.  Brushwood  and 
standing  timber  most  often  screen  the  enemy's  advance  and  steps 
should  be  taken  to  remove  them. 

44. — Tlie  tools  usually  employed  in  felling  heavy  timber  are  the 
ax  and  the  log  saw,  the  former  being  the  most  common,  although 
inexperienced  men  acquire  familiarity  with  the  latter  more 
quickly.  When  using  the  ax  the  cut  should  be  commenced  on 
the  side  toward  which  it  is  desired  the  tree  should  fall,  ropes 
being  used  to  incline  it  in  that  direction,  if  necessary;  if  immater- 
ial which  way  the  tree  falls,  then  attack  it  on  the  side  toward 
which  it  leans;  after  cutting  it  a  little  more  than  half  through 
change  over  to  the  other  side  and  commencing  about  six  inches 


32  Clearing  the  Ground. 

higher  up,  cut  until  it  falls.  In  using  the  saw  it  may  be  necessary 
to  wedge  the  cut  or  use  other  means  in  order  to  keep  the  saw 
free:  the  teeth  should  be  set  wide. 

Both  saw  and  ax  may  be  used,  in  which  case  the  ax  should  be 
used  on  the  side  toward  which  the  tree  is  to  fall  and  the  saw  on 
the  other  side.    (PL  6.) 

45. — Trees  would  ordinarily  be  cut  within  a  foot  of  the  ground 
because  a  greater  height  would  afford  cover.  A  man  should  cut 
down  a  hard  wood  tree  1  ft.  in  diameter  in  10  minutes  and  one  of 
soft  wood  of  the  same  size  in  one  third  the  time.  The  hand  ax, 
hand  saw,  and  hunting  knife  are  useful  in  felling  small  trees, 
ropes  being  attached  to  bend  them,  and  the  cut  being  made  on 
the  convex  side. 

Felled  timber  must  be  removed,  if  of  such  a  size  as  to  afford 
shelter  to  the  enemy.  It  is  utilized  in  making  field  casemates, 
magazines,  etc. 

46. — Briisliwood  can  be  cleared  at  the  rate  of  about  12  sq. 
yards  per  man  per  hour.  The  men  should  be  extended  at  about 
4  paces  interval,  using  the  bush  hook,  hatchet,  or  hand  ax,  to- 
gether with  the  gabion  or  hunting  knife. 

47. — Grain,  grass,  or  \^eeds  must  be  trampled  by  men  in 
line,  mowed,  or  burnt. 

48. — Hedges,  fences,  and  walls,  if  not  perpendicular  to  the 
front,  must  be  removed.  Live  hedges  should  be  pulled  to  one 
side  in  order  to  give  the  axmen  greater  freedom.  (PI.  6.)  Fences 
can  ordinarilly  be  demolished  with  axes,  walls  by  battering  them 
down  or  blowing  them  down  with  explosives.     (Chapter  XX.) 

Buildings  may  be  battered  down,  burned,  or  demolished  by 
explosives  according  to  circumstances.  In  the  case  of  buildings 
and  walls  it  will  usually  be  necessary  to  remove  the  debris,  which 
can  be  used  for  filling  hollows. 


PLATE  6. 


Cutter. 


\:-)f — ' — \,rv4vvvvvvvVvvvwvvvvvTA>  VW  ^s^' 


J^tnkGcl  /^olltnnr  S'cLU/ 


Ig. 


.AuQ-Lir. 


o 


"^    Infantry        Sncxcte. 


EUROPEAN. 


.M^ 


% 


""'^^^ 


PLATE  7. 


Figure  1. 


Figure  2, 


Figure  l^f    '^'  """ 


CHAPTER  TI.— Obstacles. 


49. — Obstacles  have  for  their  object  the  holding  of  the  enemy 
under  fire  while  checking  his  advance  and  breaking  up  his  for- 
mation. 

(1)  They  must  be  within  the  effective  zone  of  the  defenders' 
fire  and  must  be  so  arranged  as  to  offer  the  least  obstacle  possible 
to  an  advance  from  the  side  of  the  defense. 

(2)  They  must  be  concealed  as  far  as  possible  from  the  view  of 
the  assaulting  party,  so  that  they  may  come  upon  them  as  a  sur- 
prise. 

(3)  They  must  be  difficult  of  removal  under  fire,  and,  if  possi- 
ble, should  be  of  such  construction  as  will  necessitate  the  use  of 
tools  not  usually  carried  by  troops. 

(4)  They  should,  if  possible,  be  so  placed  as  to  be  secure  from 
the  fire  of  the  enemy's  artillery,  and  so  constructed  that,  if  struck 
by  his  projectiles,  they  will  suffer  small  damage. 

(5)  They  must  offer  no  shelter  to  the  enemy. 

50. — Abatis,  on  account  of  the  ease  with  which  it  can  be  con- 
structed, is  the  obstacle  most  used. 

It  consists  of  branches  of  trees  about  15  feet  long,  laid  on  the 
ground,  butts  pointing  to  the  rear,  all  small  twigs  being  cut  off, 
and  all  large  branches  pointed  and  interlaced.  The  abatis  should 
be  5  feet  high. 

The  branches  are  secured  to  the  ground  by  forks,  wire,  or  by 
logs  laid  over  the  butts  of  the  branches.  The  use  of  wire  to  hold 
down  the  branches  is  recommended,  and  when  used  should  be 
also  passed  from  branch  to  branch  so  as  to  form  an  extra  form  of 
entanglement.  When  more  than  one  row  of  abatis  is  used  the 
branches  of  one  row  overlap  the  butts  of  the  next  one  in  front. 
(PI.  7,  Figs.  1  and  2.) 

The  abatis  most  easy  of  construction  is  that  made  by  felling 


'38  Obstacles. 

trees  towards  the  enemy  in  such  manner  as  to  leave  the  fallen 
part  still  attached  to  the  stump,  the  branches  are  then  pointed  as 
described  before.     (Fig.  5.) 

51.— Abatis  is  often  placed  in  the  front  of  works  when  the 
ditch  is  so  shallow  as  to  present  little  or  no  obstacle  to  an  assault. 
When  so  used  they  are  placed  upright  and  well  tamped  in.  In 
all  cases,  especially  when  small  branches  are  used,  it  is  better  to 
sink  the  butts  in  triangular  pits,  and,  when  the  branches  are  in 
place,  fill  in  with  earth  and  tamp  well.     (Figs.  3  and  4.) 

In  all  cases  where  exposed  to  artillery  fire  a  glacis  should  be 
constructed  in  front  of  an  abatis,  so  as  to  protect  it  from  injury. 

52. — Ijow  Wire  entanglements  are  formed  by  driving  into  the 
ground  stakes  about  18  in.  long.  The  stakes  should  be  driven  in 
rows  about  6  feet  apart,  the  stakes  in  each  row  being  opposite  in- 
tervals in  adjacent  rows.  The  heads  of  the  stakes  are  connected 
by  stout  wire  wound  around  them.  To  make  this  more  effective, 
do  not  clear  the  ground,  but  allow  bushes,  brush,  etc.,  to  remain 
in  place.  (Fig.  6.)  Use  1  ft.  of  wire  to  1  sq.  foot  of  ground  covered. 

5.3. — Ilio-li  Wire  entanglements  are  constructed  in  the  same 
manner,  except  that  the  stakes  should  be  at  least  4  ft.  high,  and 
placed  6  to  8  feet  apart.  The  head  of  each  stake  is  connected 
with  the  foot  of  the  stake  diagonally  opposite,  the  line  of  posts  in 
front  and  rear  being  finished  off  as  fence  panels  with  barbed 
wire.  The  use  of  barbed  wire  is  not  advised  for  the  interior 
crossed  work  on  account  of  the  danger  and  difficulty  in  working 
with  it. 

Roughly,  one  yard  of  wire  is  necessary  for  each  square  foot  of 
entanglement.  Ten  men  can  make  about  9  square  yards  of  this 
entanglement  in  one  hour.  This  work  does  not  require  trained 
men.  Wire  entanglement,  either  high  or  low,  is  useful  on  the 
glacis  of  field  works,  as  it  holds  the  attacker  under  fire  at  the 
most  favorable  point.     (Fig.  7.) 

54. — Palisades  consist  of  rows  of  trunks  of  trees  or  of  squared 
trunks,  8  or  10  feet  high,  planted  close  together  and  pointed  on 
top.  When  material  is  at  hand,  ribband  pieces  should  be  spiked 
on  the  inside  along  their  tops  about  a  foot  or  two  below  the 
points  to  hold  them  steady.  They  are  used  to  advantage  in  the 
bottoms  of  ditches  or  to  close  the  gorge  of  field  works.  (PI.  8, 
Fig.  1.) 


PLATE  8. 


1! 


Fioure     1 


Figure  2 


Obstacles.  41 

55. — Fraises  are  palisades  arranged  horizontally  or  much  in- 
clined and  are  much  used  at  the  foot  of  the  exterior  slope  and  at 
the  top  of  the  counterscarp;  in  the  first  position  they  point  down 
and  in  the  second  upward.  In  each  case,  the  ribband  or  strip  is 
spiked  on  and  laid  against  the  ground  near  the  edge  of  scarp  or 
counterscarp,  as  the  case  may  be,  another  one  being  spiked  to  the 
inner  end  of  the  fraise,  thus  the  outer  ones  give  good  bearing  sur- 
faces and  do  not  break  up  the  crest,  and  the  inner  one  gives  a 
bearing  for  staking  and  tying  down.  The  slopes  described  above 
are  given  so  that  unexploded  shell  will  always  roll  away  from  the 
parapet.    (PI.  7,  Figs.  9,  10,  12  and  13.) 

Fraises  may  with  advantage  be  made  of  barbed  wire  in  the 
form  shown,  care  being  taken  that  all  wire  when  finished  is  on 
top  of  the  wooden  supports.  The  advantage  of  this  variety  of 
fraise  is  that  it  is  little  damaged  by  artillery  fire  and  is  very  diffi- 
cult of  removal. 

When  time  is  pressing  fraises  may  be  made  of  branches  of  trees 
with  the  butts  well  sunken  and  staked  down. 

5G. — Crow ^^  feet ^  Chevaux-de-frise,  and  planks  full  of  spiken 
have  been  used  in  the  past  as  obstacles  to  an  advance,  but  the 
two  former  are  not  now  issued  for  use  in  our  service,  and  the  lat- 
ter is  one  not  easily  made  in  the  field.  Such  obstacles  require 
much  time  and  material  in  their  construction  and  are  not  treated 
of  here,  as  they  do  not  fall  properly  in  the  domain  of  Field  En- 
gineering ;  their  value  in  any  event  is  not  commensurate  with 
the  difficulty  of  their  preparation.     (PI.  8,  Figs.  2  and  6.) 

57.— Small  Pits  are  square  on  the  top,  3  feet  on  a  side,  and 
are  pyramidal  in  shape ;  they  are  2  ft.  6  in.  deep,  and  have  a 
pointed  picket  driven  in  the  center  of  each. 

In  digging  these  pits  a  glacis  should  be  formed  in  front  of  the 
row  nearest  the  enemy  and,  to  avoid  filling  the  pits  with  earth 
thrown  from  the  others,  the  row  farthest  from  the  glacis  should 
be  commenced  first.  One  man  can  make  10  pits  per  day  in  easy 
soil.     (PI.  7,  Figs.  8  and  11.) 

Small  pits  may  be  surmounted  by  a  low  wire  entanglement, 
making  a  very  serious  obstacle. 

58.— Fords  may  be  made  impassable  by  strewing  them  with 
harrows,  points  up. 

59. — A  Foiig-ass  is  a  mine  so  arranged  that  upon  explosion  a 
large  mass  of  stones  or  shells  are  projected  towards  the  enemy. 
(PL  8,  Fig.  3.) 


42  ()i;sT.\('i.i:s. 

To  make  a  fougass,  dig  a  hole  in  the  shape  of  a  frustum  of  a 
cone,  inclining  the  axis  in  the  direction  of  the  enemy,  so  as  to 
muke  an  angle  with  the  horizon  of  about  45  degrees.  The  sides 
should  splay  outwards  at  an  inclination  of  12  degrees  from  the 
axis.  The  powder  charge  is  placed  in  the  bottom  of  the  hole — 
preferably  in  a  box — and  in  front  of  this  a  platform  of  wood  about 
three  inches  in  thickness :  on  this  are  piled  stones,  brick,  etc. 
The  mine  is  exploded  by  means  of  electricity  or  common  fuse. 
Care  must  be  taken  in  digging  the  hole  for  the  fougass  that  the 
line  of  least  resistance  is  in  all  cases  in  the  axis  of  the  hole,  to  he 
sure  of  tJn'ii,  throic  the  excavated  earth  upon  the  crest  towards 
the  defenders'  side  and  ram  well,  allowing  earth  tj  enclose  the 
sides  of  the  excavation  in  the  manner  shown  in  cut. 

Fougasses  are  useful  in  defending  boat-landings,  roads,  etc. 

The  following  empirical  formula  may  be  taken  for  determining 
the  charge  of  powder  for  fougasses  :  P  =  jS^,,  in  which  P  and  s 
represent  the  weight  in  pounds  of  the  powder  and  stone. 

When  broken  up,  a  cubic  foot  of  limestone  weighs  96  lbs. 

GO. — Ijaiid  Mines  are  small  mines  placed  in  the  line  of  ad- 
vance of  the  enemy  and  exploded  either  by  electricity  or  fuse 
from  the  defense.  The  small  mines  are  made  by  digging  holes 
from  2  ta  3  yards  deep,  placing  the  charge  in  a  box  in  a  recess 
excavated  in  one  side  of  the  hole,  and  refilling  with  the  excavated 
earth,  tamping  well.  The  wires  are  carried  back  in  a  small  trench 
to  the  work.  In  common  earth,  the  charge  for  2  yards  deep  is 
about  25  lbs.,  and  for  3  yards  deep  about  80  lbs.;  the  diameter  of 
the   crater  formed    will     be   about   twice   the   depth   of    charge. 

(Fig.  4.) 

01. — Barricades  are  used  to  prevent  the  passage  of  the 
enemy  through  roads,  streets,  and  defiles  generally. 

They  may  be  made  of  any  material  at  hand,  paving  stones,  over- 
turned carts,  barrels  filled  with  earth,  stones,  and  articles  of  like 
nature.  They  should  be  built  so  that  a  passage  is  always  left  for 
the  defenders,  but  means  should  be  at  hand  tj  close  the  opening 
quickly — a  wagon  may  bo  used  for  this  purpose,  being  drawn 
away  from  the  openinn-  w  lien  a  passtinc  is  desired. 

The  houses  on  either  side  should  be  looi^-holed  and  uschI  to 
flank  the  defense.  Overturned  wagons,  broken  furniture  aiul 
debris  from  the  adjacent  houses  make  a  very  good  <)J><itavh'  ami 
should  be  placed  in  front  of  the  Ijanicadc  1  >  wai.l  oil"  caxalry 
charges.     (Fig.  5. ) 


PL  ATE.  9. 


CHAPTER  Til.     Field  Works. 


02. — When  a  position  is  to  be  held  for  a  considerable  period  and 
when  time  is  available,  more  deliberate  defenses  than  the  Hasty 
or  Battle  Intrenchments  (Chapter  IV)  are  constructed.  These  are 
known  as  Field  Works  and  usually  require  a  minimum  of  6  hours 
for  construction.  The  conditions  to  be  fulfilled,  besides  those 
necessary  for  a  defensive  position  (Chapter  I),  are 

(1)  That  they  must  afford  protection  against  both  rifle  and  ar- 
tillery fire. 

(2)  That  they  must  be  of  suitable  size  for  the  garrison  that  is 
to  occupy  them. 

(8)  That  they  should  have  suitably  constructed  casemates  to 
shelter  the  garrison  at  night. 

Field  works  may  be  constructed  for  the  defense  of  a  single  ob- 
ject, as  a  bridge,  a  ford,  etc.,  or  they  may  occupy  the  key  points  in 
a  long  line  of  defense,  in  which  case  they  should  be  located  so  as 
to  afford  mutual  protection,  the  intervening  space  either  being 
left  open  or  occupied  by  shelter  trenches. 

Before  proceeding  to  the  study  of  Field  Works,  a  brief  synopsis 
of  the  technical  terms  used  in  connection  with  them  will  be 
necessary. 

63. — A  Parapet  is  a  bank  of  earth  thrown  up  to  cover  the 
defenders  while  firing. 

64.— Tlie  Trace  of  a  work  is  its  outline  in  plan:  the  term  is 
often  applied  to  the  horizontal  projection  of  its  interior  crest. 
(PL  9,  Fig.  1.) 

65. — Tlie  Profile  is  a  cross-section  of  the  work  made  by  a 
plane  perpendicular  to  the  interior  crest.     (Fig.  2.) 

In  the  profile,  the  various  parts  are  named  as  follows: 


in  FiKLi)   Works. 

a.  Banquette  slope,  e.  Exterior  slope,  d.  Ditch. 

b.  Banquette  tread,  f.  Berm.  i.  Interior  t^loiH"  of  glacis. 

c.  Interior  slope.  g.  Escarp.  k.  Glacis. 

d.  Superior  slope.  h.  Counterscarp.  t.  Trench. 

(>().  Tlie  Intorior  CiH'st  is  the  intersection  of  the  Interior 
and  Superior  elopes:  somc'iincs  cjilled  the  mjigistral  line,  ('^a'' 
Fig.  1.) 

07.  V\\r  Kxterior  Crest — that  of  the  Superior  and  Exterior 
sloix's.  c'l)"  Fig.  1.)  The  thickness  of  parapet  is  the  horizontal 
distance  between  interior  and  exterior  crests. 

08. — A  Traverse  is  a  bank  of  earth  inside  a  work  to  protect 
some  poition  of  it  from  direct  fire.  When  the  protection  afforded 
is  from  revet:  c  tire,  the  traverse  is  sometimes  called  a  Parados. 
(Figs.  3  and  1.) 

09.  All  Kinhrasiire  is  a  revetted  opening  in  the  parapet, 
through  wliich  tield  guns  may  tire.  It  is  said  to  be  Direct  or 
()i)li(iu(^  aocoi-ding  to  whctlKM-  its  axis  is  perpendicular  or  inclined 
to  the  JiiK^  of  ])arapet. 

70.  A  (inn  Bank  nv  (  im  TG|iaii1r  mi  »ii  is  a  raided 
mound,  by  means  of  which  held  guns  may  hre  over  the  i)ara|:et. 
Guns  thus  placed  are  said  to  be  "en  barbette." 

The  relative  advantages  of  Embrasures  and  Gun  Banks  are  as 
follows: — 

Embrasures  afford  greater  protection  to  the  gunners,  but 

(a)  They  afford  a  very  limited  field  of  lire. 

(b)  They  weaken  the  parapet  and  require  frequent  repairs. 

(c)  The  place  of  the  gun  when  not  in  action  cannot  well  be 
used  by  Infantry. 

The  conditions  as  to  Gun  Banks  are  the  converse  in  each  case. 

71. — Tlie  Coniniaiid  of  a  work  is  the  height  of  its  interior 
crest  above  the  ground  on  which  it  is  constructed,      ("m"  Fig.  2.) 

72. — Its  Relief  is  the  height  above  the  bottom  of  the  ditch, 
("o"  Fig.  2.) 

73. — Tlie  l*lane  of  Site  is  a  plane  tangent  to  the  ground 
on  which  the  work  is  constructed. 

14, — Tlie  Terre])leiii  is  the  surface  of  the  ground  inside  the 
work  and  does  not,  of  necessity,  coincide  with  the  plane  of  site, 
since  the  whole  interior  of  the  work — /.  c,  the  terreplein  may  l)e 
lowered  for  the  purpose  of  securing  more  cover. 


Field  Works.  47 

When  the  banquette  tread  is  more  than  two  feet  above  the  ter- 
replein,  its  slope  may  be  stepped  with  fascines  or  planks:  this  has 
the  advantage  of  giving  more  interior  space  but  tends  to  produce 
confusion  on  the  part  of  the  defenders,  especially  in  a  night 
assault. 

75. — Tlie  interior  slope  is  usually  made  as  steep,  up  to  four 
on  one,  as  the  revetment  will  stand. 

70. — Tlie  superior  slope  is  necessary  in  order  to  secure  the 
best  lire  effect  on  the  ground  immediately  in  front  of  the  work. 
It  weakens  the  parapet  near  the  interior  crest,  however,  and  this 
defect  increases  as  the  slope  is  made  steeper,  hence,  it  should  be 
as  slight  as  is  consistent  with  good  tire  effect. 

The  degree  of  this  slope  is  regulated  by  the  principle  that  fire 
from  rifles  resting  on  its  surface  should  not  pass  more  than  three 
feet  above  the  glacis,  or,  when  there  is  no  glacis,  above  the  outer 
edge  of  the  ditch.     It  will  thus  depend  on 

(1)  The  command  of  the  work. 

(2)  The  inclination  of  the  plane  of  site. 

(3)  The  distance  from  the  interior  crest  to  outer  edge  of  ditch. 
The  slope  should  not  exceed  one  on  four;  one  on  six  (normal)  is 

better,  and  then,  if  necessary,  make  a  glacis  of  the  requisite 
height. 

77. — Tlie  exterior  slope  should  be  as  gentle  as  two  on  three, 
if  possible,  owing  to  the  fact  that  steeper  slopes  are  soon  destroyed 
by  artillery  fire.  ^  ' 

78. — Tlie  Berni  may  be  as  great  as  6  ft.  in  width;  ordinarily  it 
would  not  be  greater  than  2  ft.,  while  in  favorable  soil  none  may 
be  left  at  all. 

Advantages  of  berm. 

(1)  It  relieves  the  edge  of  the  ditch  from  the  weight  of  the  par- 
apet and  thus  prevents  caving,  in  loose  soil.  ^cf^i- 

(2)  It  enables  the  parapet  to  be  thickened.  ffrx       ^'  />     '^/^ 

Disadvantages:  vC^      o^        -^TV 

(1)  It  affords  a  footing  in  an  assault.     (This,  however^lHl^.3^oy^NIA. 

partially  remedied  by  use  of  obstacles.)  ~ 

79. — The  slope  of  the  escarp  and  counterscarp  should  be  equal 

to  or  greater  than  the  exterior  slope,  the  latter  being  as  steep  as 

the  earth  will  stand. 


18  Field  Works. 

80.  Tlie  CMcicis  should  be  parallel  to  the  superior  slope,  in 
order  to  get  the  best  fire  effect  from  the  crest. 

81. — If  the  parapet  does  not  require  much  earth,  and  the  ditch 
is  required  as  an  obstacle,  it  may  be  made  triangular  in  cross  sec- 
tion. This  form  gives  the  greatest  depth  and  prevents  the  assail- 
ants from  forming  in  the  ditch,  but  it  is  difficult  of  construction. 
Eight  feet  may  be  taken  as  the  cxticnic  depth  of  ditch  and  twelve 
feet  as  the  extreme  height  of  ])araiJot.  The  width  of  the  ditch 
varies  with  the  amount  of  earth  required — 1'2  ft.  at  tlie  top  being 
a  minim u in. 

A  parajrt  with  trench  and  ditch  affords  cover  in  the  shortest 
time  possible:  each  foot  of  depth  in  the  trench  means  2  ft.  of 
cover,  plus  the  additional  protection  afforded  by  the  earth  from 
the  ditch. 

A  parapet  with  ditch  alone  affords  greater  cover  to  the  ground 
in  rear  and  better  command  of  ground  in  front,  but  its  height 
makes  it  more  conspicuous. 

82.-"Ref erring  to  traces  of  various  works  (PI.  9,  Fig.  5.)— 

a,  is  a  salient  angle, 
a'     is  a  shoulder  angle. 

b,  is  a  re-entrant  angle. 

c,  c,  c,     are  faces.  e,  e,     is  the  gorge. 

d,  d,  d,     are  flanks.  f,     is  the  capitnl. 

83.— Field  Works  are  classified  wuth  reference  to  their 
trace,  as 

(1)  Open,  which  have  thick  parapets  on  exposed  sides,  the  rear 
or  gorge  being  open. 

(2)  Closed,  in  which  the  thick  parapet  is  continuous. 

(3)  Half -Closed,  which  only  differ  from  the  "open"  in  that 
the  gorge  is  closed  by  obstacles,  stockade  work,  or  shelter 
trenches. 

Advanced  works  within  rifle  range  of  the  main  defensive  line, 
as  well  as  those  in  positions  where  the  flanks  are  secure  (as  a 
bridge  head),  should  usually  be  "open."  Works  in  main  line  and 
advanced  works  beyond  rifle  range  should  be  "  half -closed;  *'  those 
in  isolated  positions  or  on  the  flanks  of  a  defensive  line— "closed." 

Open  works  have  the  advantage  over  closed,  of  affording  greater 
freedom  of  movement  to  the  defenders,  and,  in  the  event  of  cap- 
ture, of  being  exposed  to  fire  and  assault  from  the  works  in  rear. 


PLATE  10. 


Field  Works.  51 

Closed  works,  while  affording  greater  protection  from  assault, 
are  liable  to  have  their  parapets  exposed  to  enfilade  or  reverse 
fire,  besides  which  the  available  interior  space  is  much  reduced. 

84. — Forts  and  Redoubts  (Closed  Works)  are  distinguished 
by  the  former  having  re-entering  angles,  thus  affording  defense 
of  the  ditch  from  the  parapet,  both  conditions  being  lacking  in 
redoubts. 

Redoubts,  as  compared  to  forts,  are  of  simpler  trace,  do  not  re- 
quire so  large  a  garrison,  and  afford  better  frontal  fire;  but,  as 
they  have  no  ditch  defense  (unless  caponiers  and  counterscarp 
galleries  are  constructed),  they  should  be  traced  to  support  one 
another. 

85. — With  respect  to  caponiers  (PI.  20)  and  counterscarp  galler- 
ies— the  former,  if  sunken,  as  is  usually  necessary  for  protection 
against  artillery  fire,  may,  become  untenable  in  rainy  weather; 
while  communication  with  the  latter  is  difficult  and  may  by  the 
enemy,  be  rendered  impossible.  The  objections  to  these  forms  of 
ditch  defense  are  so  great,  and  their  use  so  limited,  where  proper 
frontal  fire  and  obstacles  are  possible,  that  their  construction  is 
seldom  necessary. 

86. — Tlie  Sector  of  Fire  is  a  term  used  to  designate  the  an- 
gular space  in  front  of  a  work  which  is  swept  by  its  fire  (30°  on 
each  side  of  a  perpendicular  being  considered  the  limit  of  oblique 
rifle  fire.)  Thus,  a  straight  line  of  parapet  has  a  sector  of  fire  of  60° 
(PI.  10,  Fig.  1),  while,  in  a  redan,  it  varies  with  the  angle  at  the 
salient.  With  a  salient  of  120°,  the  sector  of  fire  is  evidently  120° 
(Fig.  2),  with  a  60°  salient,  there  will  be  an  undefended  space  of 
60°.  (Fig.  3.)  This  undefended  space  may  be  done  away  with  by 
blunting  the  redan.  (Fig.  4.)  A  redan  with  shoulder  angles  (Fig.  5) 
furnishes  a  ditch  defense  in  front  of  the  shoulders  and  doers  away 
with  part  of  the  dead  space  in  front  of  the  salient  but  it  is  diffi- 
cult of  construction  and  is  not  usually  resorted  to. 

87. — For  reasons  given  in  Chapter  XI,  it  is  often  desirable  to 
place  the  guns  outside  the  work;  in  which  case  some  plan  like 
Fig.  6,  may  be  adopted,  the  single  line  representing  a  shelter 
ti-ench. 

88.— Defilade  of  Field  Works.  In  order  that  Field  Works 
may  fulfill  the  condition  of  screening  the  occupants  from  the  fire 
aiul  \  lew  of  an  enemy,  the  problem  of  defilade  arises. 


VJ  Field  Wokks. 

This  may  be  defined  as  the  operation  of  regulating  the  direction 
and  command  of  the  earth  cover  so  that  the  interior  of  the  work 
is  protected  from  the  direct  tire  of  an  enemy. 

The  problem  resolves  itself  into  two  distinct  parts — 

(1)  Defilading  in  plan. 

(2)  Defilading  in  section. 

89.— ^Defilacliiiji'  in  i)laii.  Tliis  involves  the  selection  of  the 
trace  of  the  work  (its  ijosition  having  been  previously  chosen.) 
The  trace  will  vary  with  the  plane  of  site,  the  terrain  in  the  im- 
mediate vicinity,  the  x^i'oximity  of  high  ground  that  the  enemy 
may  occupy,  and  the  time  available  for  construction.  A  plane  of 
site  sloi)ing  to  the  rear  is  obviously  the  easiest  to  defilade,  and 
one  sloi)ing  toward  the  enemy,  the  most  difficult.  Salients  should 
occupy  commanding  ground,  the  lower  portion  being  taken  for 
the  re-entrants  or  for  th«  gorge.  The  longer  faces  of  a  work 
should  lie  in  the  direction  of  lower  or  inaccessible  ground,  so  that 
they  connot  be  enfiladed. 

With  commanding  ground  in  front,  the  work  is  more  difficult 
to  defilade  in  proportion  to  its  depth,  therefore,  have  longer  faces 
opposed  to  the  high  ground  and  make  the  work  as  shallow  as  is 
consistent  with  other  conditions. 

As  a  rule,  the  longer  faces  of  a  work  must  lie  so  that  the  de- 
fenders can  bring  as  direct  a  fire  as  possible  in  the  direction  of 
expected  attack. 

All  the  foregoing  conditions  as  to  defilading  in  plan,  cannot,  in 
the  usual  case,  be  satisfied,  but  the  object  to  be  attained  must  be 
kept  constantly  in  view,  and,  in  selecting  the  trace  for  a  work,  an 
officer's  ability  will  be  shown  by  the  skill  with  which  he  harmon- 
izes the  various  diverse  requirements. 

After  the  careful  selection  of  the  trace,  as  already  indicated, 
and  marking  it  by  pickets,  the  problem  is  completed  by  defilading 
the  proposed  work  in  section. 

90. — Deflladiiig  in  Section.  With  a  horizontal  site  and 
only  level  ground  toward  the  enemy,  a  constant  command  of  8  ft. 
is  sufficient  to  protect  the  whole  interior  of  the  work. 

On  an  irregular  site,  or  when  necessary  to  place  a  work  in  a 
position  commanded  by  higher  accessible  ground,  the  necessary 
protection  of  8  ft.  may  be  attained  in  one  of  three  ways— 

(1)  By  raising  a  parapet. 

(2)  By  lowering  the  terreplein. 


PLATE  11 


Figure  1. 


Figure.  2. 


^^ 


S^l^^^ 


c^'f^fc 


tL 


^-'-T^ 


Figure  3. 


'^0^^^^^  -/K  'i 


^^^; 


^R 


Figure  4  . 


^T;^— ::    ^l^-^^^^^Zj^^, 


Field  Works.  55 

(3)  By  use  of  traverses,  parados,  bonnets,  etc. 

To  determine  how  much  protection  is  needed,  suppose,  for  ex- 
ample, the  proposed  work  is  a  lunette.  Plant  poles  at  the  salients 
of  sufficient  length  to  reach  the  interior  crest  of  completed  work. 
Place  two  pickets  at  the  gorge,  about  6  ft.  apart,  one  on  each  side 
of  the  capital  and  a  third  8  ft.  to  the  front.  Tie  a  string  to  the 
rear  pickets,  3.5  ft.  from  the  ground,  the  string  passing  round  the 
third  stake.  (PI.  11,  Fig.  2.)  Taking  position  behind  the  horizontal 
string,  have  an  assistant  move  the  string  on  the  forward  picket 
until  it  comes  into  the  plane  fixed  by  the  eye,  the  horizontal 
string  and  the  highest  point  of  the  dangerous  ground.  This  plane, 
which  is  now  established  by  the  string  triangle,  is  called  the  tan- 
gent plane.  A  plane  parallel  to  this  and  4.5  ft.  above  it  is  known 
as  the  plane  of  defilade.  (Fig  1.)  The  proper  height  of  parapet  at 
the  salient  and  shoulder  angles  is  now  fixed  by  sawing  off  the 
poles  4.5  ft.  above  the  points  in  which  the  tangent  plane  cuts 
them.  This  will  evidently  give  8  ft.  cover  at  the  gorge,  at  which 
point  the  height  of  parapet  of  the  flanks  is  8  ft. 

If  it  is  found  that  the  required  height  of  parapet  exceeds  12  ft., 
the  plane  of  defilade  may  be  lowered  not  to  exceed  1.5  ft.  This 
will  still  give  6.5  ft.  protection  at  the  gorge. 

If  this  proves  insufficient,  either  traverses  must  be  resorted  to 
or  the  terreplein  at  the  gorge  lowered. 

91. — To  defilade  a  Avork  from  two  or  more  lieiglits, 
the  plane  must  be  tangent  to  the  two  heights  to  which  angles  of 
elevation  are  the  greatest.  As  three  points  fix  a  plane,  it  follows 
that  the  tangent  plane  would  usually  contain  but  a  single  point 
of  the  string  at  the  gorge,  hence,  the  problem  is  solved  by  revers- 
ing the  string  triangle — i.  e.,  fixing  the  apex  at  the  gorge  3.5  ft. 
above  the  ground,  and  the  two  extremities  of  the  base  within  the 
the  proposed  work  and  far  enough  apart  to  allow  the  two  heights  to 
be  seen  between  them.  An  assistant  at  each  of  the  forward  stakes 
adjusts  the  string  as  directed.  (Fig.  3.)  The  problem  is  then  com- 
pleted as  in  the  previous  case. 

92. — It  is  sometimes  advisable,  when  a  single  plane  of  defilade 
gives  too  great  a  command,  to  use  two  planes  ;  the  portion  of  the 
interior  of  the  work  on  the  side  toward  H  (Fig.  4)  being  defiladed 
from  it,  and  that  on  the  other  side  from  the  height  H'.  This 
method  exposes  the  faces  and  flanks  to  reverse  fire  and  renders 
traverses  (parados)  necessary. 


.'it')  |-'l  1,1.1)    WolJKS. 

J>:3. — The  lieio^lit  of  a  traverse  (which  should  be  such  that 
a  shot  grazing  it  will  pass  2  ft.  above  the  parapet  it  is  to  cover)  is 
found  as  follows : 

Assume  that  the  traverse  is  to  be  on  the  capital  of  a  lunette. 

The  problem  of  direct  defilade  with  two  planes  having  been 
solved,  and  the  poles  at  angles  of  the  works  having  been  sawed  off 
to  indicate  the  proper  height  of  interior  crest  in  order  to  defilade 
the  work  as  far  as  the  cai)ital,  the  height  of  traverse  to  protect  a 
flank  from  reverse  fire  is  found  thus :  Measure  down  from  the 
tops  of  the  poles  at  the  extremities  of  the  flank  any  convenient  dis- 
tance, as  3  feet,*  mark  the  points  and  connect  them  by  a  string. 
This  string  and  the  opposite  height  determine  a  plane  which  will 
cut  rods  held  vertically  on  the  capital,  at  a  distance  of  5  feet  below 
the  required  top  of  the  traverse  (2  ft.  plus  the  distance  measured 
down  on  the  poles).  Proceed  in  a  similar  manner,  using  the  other 
hill  and  its  opposite  flank.  The  greater  of  the  two  results  fixes 
the  height  of  that  portion  of  the  traverse.  In  the  same  manner, 
its  height  to  protect  the  faces  from  reverse  fire  may  be  found. 
By  reference  to  Fig.  4  this  will  be  readily  understood. 

This  method,  while  not  absolutely  accurate,  will  give  results 
near  enough  for  all  jn-actical  purposes,  with  the  error  on  the  side 
of  safety.  Traverses  or  Parados  are  the  usual  protection  against 
reverse  and  enfilade  Ww.  and.  although  sometimes  used  to  protect 
parts  of  a  work  from  direct  lire,  this  is  usually  attained  either  by 
raising  the  para,pet,  by  low^ering  the  terreplein,  or  by  both  these 
methods  combined. 

94. — Profiling.  After  the  trace  of  the  work  has  been  decided 
upon,  the  problem  of  defilade  solved,  the  poles  at  the  angles  cut 
off  as  indicated,  and  the  cross  saction  of  the  parapet  decided 
upon,  the  next  step  is  to  erect  profiles  which  shall  correspond  to 
this  cross  section.  Thes3  profiles  are,  if  practicable,  to  be  made 
of  strips  or  battens,  1  in.  x 2  in.  and  placed  at  intervals  of  about  10 
yds.  along  each  face  and  flank,  as  well  as  at  each  angle. 

For  parapets  not  over  6  ft.  in  height,  stakes  may  at  once  be 
driven  into  the  ground  and  strips  nailed  to  them,  but  for  higher 
parapets  it  is  more  convenient  to  make  the  profile  on  the  ground, 
merely  driving  short  pickets  in  ijlace  of  the  long  stakes  in  the 
first   instance.      When   completed,  the   profile   is   up-ended    and 

*  The  idea  being  to  have  the  string  behind  which  tlie  obstivtr  stands,  when  looking 
towards  the  height,  at  about  the  level  of  the  eye. 


PLATE  12. 


PLATE  13 


Field  Works.  61 

nailed  to  the  pickets.  (PI.  12,  Fig.  1.)  If  strips  cannot  be  ob- 
tained, the  entire  profile,  except  the  uprights,  may  be  made  of 
twine.  The  profiles  at  the  angles  of  the  works,  known  as  oblique 
or  angle  profiles,  will  evidently  differ  from  the  others  in  length, 
while  their  height,  on  level  ground,  remains  the  same.  The  posi- 
tion of  any  point  of  the  angle  profile,  as,  for  example,  the  exterior 
crest,  is  fixed  by  finding  the  intersection  of  the  prolonged  exterior 
crest  lines  of  the  face  profiles.  This  result  is  accomplished  by 
standing  on  the  farther  side  of  the  sacond  profile  from  the  angle 
and  lining  in  an  assistant  who  holds  a  rod  vertically  at  the  angle, 
one  end  of  the  rod  resting  on  the  ground.  Aftar  the  profiles  are 
in  place,  twine  should  be  stretched  between  them  to  indicate  the 
various  crest  lines.  The  outer  edge  of  the  battsns  marks  the 
extent  of  the  fill,  except  in  the  case  of  the  intarior  slope,  which 
is  marked  by  the  inner  edge  when  the  slope  is  to  be  revetted. 

95. — Calculation  of  Dinieiisioiis  of  Eartli works.  The 
command  of  the  propos3d  work  having  been  fixed  by  the  require- 
ments of  defilade,  and  the  thicknesH  by  the  character  of  fire  ex- 
pected, it  becomes  necessary  to  calculate  the  dimensions  of  the 
excavations^  so  that  they  ivill  furnish  enough,  and  no  more, 
earth  than  is  required.  The  size  of  embankments  and  trench  are, 
by  the  nature  of  the  problem,  fixed,  as  is  the  depth  of  ditch,  hence 
the  only  variable  is  width  of  ditch,  which  is  found  as  follows: 

Assuming  the  relief  to  be  constant  and  the  profile,  for  example, 
to  be  as  shown  in  PL  13,  make  a  sectional  sketch  of  the  proposed 
work  at  any  point  except  an  angle.  Calculate  the  sectional  area 
of  parapet,  glacis,  and  trench,  in  sq.  ft.  and  from  the  sum  of  the 
first  two  subtract  the  last:  the  remainder  divided  by  the  assumed 
depth  of  ditch,  in  feet,  will  give  the  mean  width  of  ditch, 'from 
which,  knowing  the  slope  of  escarp  and  counterscarp,  the  width 
at  top  and  bottom  can  readily  be  found. 

96. — Eartli  in  enibaiiliineiit  occupies,  for  a  time,  about 
one-twelfth  more  space  than  it  did  originally,  but  this  increase  is 
not  usually  taken  into  account  in  the  computations  for  ascertain- 
ing the  width  of  ditch.  When  the  relief  of  a  work  is  not  constant, 
it  is  evident  that,  in  order  to  get  the  proper  amount  of  earth, 
either  the  depth  or  the  width  of  ditch  must  vary.  On  account  of 
the  labor  required  in  raising  earth,  the  limit  of  depth  is  taken  at 
8  ft.;  for  a  similar  reason,  the  maximum  height  of  parapet  is 
taken  at  12  ft.    Whatever  the  depth  of  ditch  assumed,  it  is  always 


(J2  FlKLJ)    \V()IM<s. 

constant.  The  required  width  at  any  point  is  found  by  means  of 
a  section  of  the  work,  as  ah-eady  explained,  a  section  near  the 
extremities  of  each  face  determining  the  width  of  ditch  for  that 
entire  face. 

07. — An  excess  of  earth  will  occur  at  the  salients  ami  a  defi- 
ciency at  the  re-entrants,  althouijh  this  may  be  partially  obviated 
1)\   niakiiii;'  tlic  slioNclcrs  tliiMw  towni'd  the  re-entrants. 

1)8.  I)i-aiiuit»'c  <>r  tin*  trench  must  be  provided  for  at  the 
time  the  work  is  constructed.  If  the  fall  is  toward  the  goruc  an 
open  drain  will  suffice,  but,  if  in  any  other  direction,  a  covered 
drain  (PI.  50)  should  be  left  t3  carry  the  water  to  the  ditch. 

Construction  of  Fieldworks.  The  details  of  construc- 
tion and  dimensipns  of  earthworks  will  change  with  varying  re- 
quirements and  soil,  but  there  are  certain  general  principles  that 
should  be  followed  in  all. 

99.— As  to  in'ofile  :  The  Normal  (PI.  14,  Fig.  2)  fulfills  the 
conditions  as  to  simplicity,  protection  against  field  artillery  (in 
most  s  )ils).  (•  oinmand  of  the  ground  in  front,  and  cover  standing, 
ill  \]\r  trench.  The  trench  is  stepped  and  steps  revetted  to  facili- 
tate' mounting  the  banquette,  while  the  berm  is  omitted  to  deprive 
the  assailants  of  a  foothold.  The  command  may  be  increased 
either  with  or  without  constant  ijelief,  the  parapet  thickened  or 
reduced,  and  the  trench  made  into  a  casemate  without  changing 
the  type  of  this  prcflle. 

lOO. — As  to  g;arrison  :  For  ordinary  field  works,  the  garri- 
son is  usually  computed  at  2  men  per  yard  of  interior  crest ;  but 
for  isolated  works,  this  estimate  should  be  increased  by  one-half. 
Embrasures  and  gun-banks  each  reduce  the  interior  crest  line 
available  for  troops,  by  5  yards. 

lOl .— As  to  layina*  out  tasks:  Cutting  lines  must  be 
marked  l)y  tape  or  pick,  computations  made,  and  the  exact  size 
of  the  task  for  each  relief  determined  in  accordance  with  the 
rules  given  in  Chapter  VIII. 

As  an  example  of  laying  out  tasks,  assume  that  an  earthwork 
with  normal  prohle  and  constant  command  of  6  ft.  is  to  be  made 
on  a  level  site. 

Before  work  is  commenced,  the  outer  and  the  cutting  lines  of 
ditch  and  trench  must  be  marked.  As  fatigue  parties  cannot  be 
expected  to  excavate  earth  and  at  the  same  time  preserve  the 
proper  slopes,  the  usual  method  followed  is  to  dig  vertically  as  in- 


PLATE'14 


^B-d/Ui/  .    i^\  Figure  L 

■     NORMAL      PROF/LE 

SHOW/NG  TASKS. 


s. 

itUndd 

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EARTH  f/lOfif 

rHeuEF. 

rHEU£F.  \3'/i£uqF. 

Spades 

PCcJ<^ 

Sh<,veU%)^rRel 

2Rec. 

5^^ 

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~1 

PI.  14,  Table,  2d  relief,  Trench, in8ert'^2(kl"an(l"I0s"ancl  for  total"33^' 
read  "63.'^ 


PLATE  15. 


FIG.  1 


FIG.  2. 

,._  -/300     f.o  3000  yards       ^'^  — ,  /^ 


•A: 


Field  Works.  67 

dicated  by  the  cvitting  lines  and  afterward  form  the  slopes  by 
cutting  off  the  steps. 

The  cutting  lines  for  the  task  of  the  1st  Relief  would  be  made 
on  the  ground,  as  indicated  in  section  and  plan.  (PI.  14,  Fig.  1). 
The  1st  Relief  having  finished,  cutting  lines  for  task  of  2d  Relief 
would  then  be  marked  out,  and  finally,  the  3d  Relief  would  com- 
plete the  slopes  of  ditch  and  parapet,  and  finish  any  work  not 
completed  by  the  other  reliefs. 

When  not  practicable  to  revet  the  banquette  and  trench  steps, 
the  risers  may  be  sloped  back  at  about  six  on  one. 

When  necessary  to  throw  earth  more  than  12  ft.  horizontally, 
extra  shovelers  should  be  provided  at  the  rate  of  1  to  each  2,  or  2 
to  each  3  diggers,  depending  upon  the  soil  and  the  distance  it  is  to 
be  thrown. 

102. — Gun  Banks,  when  made,  are  usually  placed  in  the 
salients,  for  the  reasons  that  the  guns  will  have  a  greater  field  of 
fire  and  it  is  at  this  point  that  the  earth  of  which  they  are  made  is 
in  excess.  PI.  12,  Fig.  2  shows  a  gun-bank  on  a  straight  line  of  par- 
apet and  Fig.  3  one  at  a  salient.  The  top  is  horizontal  and  3.5  ft. 
below  the  interior  crest :  this  distance  may  vary,  however,  for  dif- 
ferent pieces.  All  slopes  are  one  on  one,  except  the  ramp,  or  road- 
way leading  up  to  the  bank ;  this  may  be  as  steep  as  one  on  four, 
but  a  gentler  slope  is  better.  The  width  of  ramp  should  be  8  ft. 
The  level  surface  of  the  bank  extends  back  24  ft.  from  the  parapet 
and  a  log  or  fascine  is  half  sunken  and  picketed  near  the  front,  for 
a  hurter.  The  width  of  bank  for  a  single  gun  is  15  ft.  At  a  salient 
(PI.  12,  Figs.  3  and  4)  the  angle  is  filled  in  by  a  straight  revetment 
from  6  ft.  to  15  ft.  long  and  the  superior  slope  reduced  to  corra- 
spond  to  lines  joining  its  extremities  with  the  exterior  crest  salient. 
This  forms  what  is  known  as  a   "pan  coup^.'' 

10.3. — Embrasures  for  field  guns  would  be  used  in  positions 
where  the  fire  is  required  to  he  in  one  direction  only ;  for  example, 
to  sweep  a  road,  bridge,  or  ford;  or  in  the  flank  of  a  work  to 
cover  ground  in  front  of  an  adjacent  work. 

PI.  15,  Fig.  1,  shows  the  horizontal  projection  and  the  section  of 
an  embrasure.  It  is  made  at  the  same  time  as  the  parapet,  by 
making  the  sole  "  s "  parallel  to  the  superior  slope.  The  cheeks, 
"c,  c,"  are  vertical<l©  the  throat,  "e,"  and  have  a  slope  of  one  on 
one  at  the  other  extremity ;  their  height  should  never  exceed  4  ft. 

The  usual  method  of  forming  an  embrasure  is  to  stretch  a  string 


()8  Field  Works. 

alon^^  the  lino  of  tiro  :  at  tlio  tliroat  lay  off  1  ft.  on  oacli  sido  of  it, 
and  at  a  distanco  of  5  ft.  from  tho  throat  lay  otf  1.")  ft.  in  a  similar 
manner.  Ki^iit  linos  joinini:-  tho  oorrosijondin^;'  points  so  doter- 
nnnod  will  mark  tho  oiitor  linos  of  tho  solo,  which  will  si)lay  one 
on  ton.  Kaoh  throat  i^ahion  is  vertical,  the  extreme  ones  hoin<i-  in- 
clined thi-oe  on  one:  tlio  slope  of  the  intermediate^  on'/s  is  secured 
l)y  alij^'nmont  to])  and  hottom  on  tho  extreme  ones.  Haoh  u-;d)i()n 
is  anchored  independently  (,f  the  otliers.  so  that  one  may  he  torn 
out  without  serioiislv  injnrinu'  tlic  ond)i'asui-e. 

1  04.  "By  tho  MiM-ioii  is  meant  that  portion  of  the  parapet  be- 
tween two  end)i'asures  and  al)o\'e  the  soles.  Knd»rasiires  should,  as 
a  rule.  no\'er  be  (dosef  toii'ethor  than  ir)ft..  ot  lierwise  thi' merlon  is 
too  much  weakened. 


PLATE  16. 


Fig.  1 


F-g-/2- 


Fig.3. 


0  .Q<..Q..   :(J..O...-Q-.i.>a.r.g^ 


'4'^' 

r       4-' 


5' 

5' 

5' 

5' 

^3!i 


Fig.4 


0 

9 


^. 


CHAPTER  VIII.— Working  Parties. 


Occasion  may  arise,  as,  for  example,  at  night,  in  the  presence  of 
an  enemy  or  even  with  a  large  working  party,  when  a  well-estab- 
lished system  of  taking  and  handling  tools,  distributing  and  reliev- 
ing working  parties,  etc.,  will  be  of  paramount  importance. 

105.  Organization  of  Working  Parties.  The  nature 
of  the  required  work  having  been  decided  upon,  the  estimate  of 
and  the  application  for  the  requisite  number  of  men  and  tools  de- 
volves upon  the  otRcer  charged  with  its  execution. 

A  working  party  of  the  requisite  strength  (which  should  include 
a  reserve  of  1-lOth)  should  be  furnished,  as  far  as  possible,  from  a 
complete  organization,  a  company,  a  battalion  or  brigade,  and  not 
from  detachments  of  different  organizations. 

106. — Ilesponsibility.  The  party  should  be  divided  into  re- 
liefs and  the  task  each  is  to  accomplish  made  plain  before  it  begins 
work.  The  officers  and  non-commissioned  officers  of  the  working 
Ijarty  are  responsible  for  the  amount  of  work  done. 

107. — Tali:ing  Tools.  The  first  relief,  having  been  formed 
in  single  rank  with  rifles  slung  across  the  back,  is  marched  to  the 
park  where  the  tools  have  previously  been  laid  out,  either  in  rows 
(PL  16,  Fig.  1)  or  in  heaps.  (Fig.  2.)  The  relief  in  the  former  case 
is  advanced  in  line  to  the  row  and  each  takes  a  pick  in  the  left 
and  a  spade  in  the  right  hand;  in  the  latter  case  the  party  in 
column  of  files  is  marched  between  the  piles,  each  in  turn  re- 
ceiving a  pick  in  the  left  and  a  spade  in  the  right  hand.  The 
relief  is  then  marched  in  column  of  fours  or  twos  to  the  point 
where  the  work  is  to  begin. 

108. — Carrying  Tools.  In  carrying  picks  and  spades  the 
handles  are  grasped  near  the  iron,  which  is  held  vertically,  the 
arms  extended  and  the  hands  close  to  the  side.  In  turning,  the 
point  of  the  pick  should  be  lowered  and  the  blade  of  the  shovel 


T2  WOKKINCJ    PAiniKS. 

raised,  and  when  marching,  either  in  line  or  in  cohuiin,  the  han- 
dles should  be  splayed  outward,  in  order  to  ])i(>v('nt  interference. 
The  necessity  under  certain  circumstances  of  preserving  silence 
makes  the  above  precautions  important  at  all  times  as  a  matter  of 
trainin^^ 

109.  Kxtciidiiio;  the  AVorkiiio-  Paity.  When  the  first 
relief  approaches  the  designated  point  it  is  halted,  then  broken  in- 
to colunm  of  files  and  direction  changed,  if  necessary,  so  that  the 
head  of  the  column  approaches  in  a  direction  parallel  to  and  about 
3  yds.  in  rear  of  the  tape  marking  the  front  edge  of  proposed  exca- 
vation. (Pig.  3.)  When  the  leading  file  is  opposite  his  place  the 
command  is  given : 

(1)  On  right  {or  left)  into  line  at  two  fxici's  interval.  (2) 
Mareli.     (3)  Detachment.    (4)  llall. 

The  command  "halt"  is  given  when  the  leading  hie  is  1  yd.  in 
rear  of  the  tape.  While  the  line  is  forming,  the  correct  positions 
are  at  once  taken,  as  follows : 

Each  man  on  arriving  at  the  line  extends  his  arms  horizontally, 
holding  them  thus  until  his  own  position  and  that  of  the  man  fol- 
lowing him  are  established  by  touching  hands.  As  soon  as  each 
man  has  his  position  he  drives  his  pick  into  the  ground  on  the 
left  of  his  own  task  and  lays  his  shovel  on  the  ground,  parallel  to 
and  at  a  distance  in  the  rear  of  the  tape  equal  to  the  width  of  his 
task  from  front  to  rear. 

Rifles  are  then  unslung.  belts  and  canteens  removed,  and  all 
having  been  placed  on  the  ground  three  paces  directly  to  the  rear 
of  task,  butts  of  rifles  toward  the  front,  tlie  men  sit  or  lie  down  be- 
hind their  shovels  until  the  order  '■('onnncncc  trorJ:." 

no. — Extension  of  2d  and  3d  Reliefs.  Each  man  of 
the  1st  relief,  after  completing  his  task,  scrapes  his  tools  and  lays 
them  together  in  rear  of  the  trench. 

The  task  being  completed,  each  man  secures  his  accoutrements 
and  rifle,  and  then,  under  direction  of  his  officers,  closes  in  to  the 
left  (or  right),  forming  column  of  fours  which  is  then  marched 
back  to  camp. 

As  an  incentive  to  rapid  work,  each  relief  should  be  allowed  to 
return  to  camp  on  the  completion  of  its  task. 

If  the  w^orking  party  be  large  and  the  work  of  a  complicated 
nature,  each  relief  should  arrive  in  successive  detachments  and 


WoRKiNd  Parties.  >   "^-(^/l^.-  ^<9^ 

their  location  on  the  work  should  have  heen  previously  desrraftted^  ^<V 
so  that  there  need  be  no  delay  or  confusion,  even  at  night.    ^^O/^. 

Work  should  not  be  commenced  until  the  distribution  of  th^J^/^- 
entire  relief  is  complete,  since  any  change  after  work  has  begun 
tends  to  confusion,  loss  of  tools,  and  delay. 

111. — Tasks.  An  untrained  workman  can  excavate  in  ordi- 
nary soil  one  cubic  yard  of  earth'  per  hour  for  four  consecutive 
hours.  As  some  men  work  slower  than  others,  however,  it  is 
usual  to  estimate  at  6  hours  per  man  for  the  lifting  of  4  cu.  yds. 
of  earth  from  a  trench  3.5  to  5  ft.  deep  and  throwing  the  same  a 
horizontal  distance  of  10  ft. 

When  it  is  necessary  to  throw  the  earth  more  than  12  ft.  hori- 
zontally, extra  shovelers  should  be  provided  for  re-handling  it,  in 
the  proportion  of  1  shoveler  to  every  2  diggers. 

When  exposed  to  the  enemy's  fire,  a  skirmish  line  is  kept  well 
to  the  front  and  the  earth  first  excavated  is  thrown  close  to  the 
edge  of  the  ditch,  forming  a  screen  which  is  gradually  thickened ; 
under  other  circumstances  the  earth  first  excavated  is  thrown 
farthest. 

Five  feet,  or  two  paces,  is  the  usual  distance  apart  for  men  to 
work,  but  they  may  be  posted  as  close  together  as  4  ft.,  while  using 
the  heavy  pick  and  shovel.  As  a  precaution  against  injury  to  ad- 
jacent workers,  the  men  should  swing  the  pick  in  a  direction  per- 
pendicular to  the  tape. 

112. — Working  parties  may  be  extended  at  less  or  greater  in- 
tervals by  making  the  corresponding  changes  in  the  commands : 
wlien  this  is  done,  it  will  usually  be  necessary  to  verify  intervals. 

When  necessary  to  complete  a  task  in  the  shortest  possible  time 
or  when  the  men  available  greatly  exceed  the  number  of  tools, 
working  parties  should  be  formed  in  double  rank,  two  men  being 
assigned  to  each  set  of  tools,  which  should  be  carried  by  the  front 
rank  man.  When  working  in  this  manner  with  a  double  relief, 
the  men,  under  direction  of  non-commiesioned  officers,  should 
change  off  every  10  or  15  minutes. 

Officers  having  general  supervision  of  the  work  should  not  be 
changed  at  the  same  time  the  reliefs  are. 

The  sizes  of  tasks  based  on  the  4  yd.  rule  may  be  arranged  as 
shown  in  diagram.  (Fig.  4.)  For  arrangement  of  tasks  in  diffi 
cult  soil  see  PI.  14. 


CHAPTER  IX.— He  vet  ting  Materials  and 
Revetments. 


1 1.*3,  A  IJevc'tiiu'iit  is  a  facintr  used  to  hold  up  an  enibank- 
ment  at  a  steeper  slope  than  it  would  assume  naturally. 

114. — Revetting  Materials.  The  revetments  most  com- 
monly used  in  field  engineering  are  made  either  of  brushwood 
in  the  rough,  fascines,  gabions,  hurdles,  planks,  timber,  sods,  sand- 
bags, pisa,  adobe,  or  of  a  combination  of  two  or  more  of  these. 

115. — Briisliwood,  which  is  used  in  making  the  first  four 
should  be  of  willow,  birch,  ash,  hickory,  or  hazel,  and  is  most  pli- 
ant when  not  in  leaf :  it  may  be  of  any  size  when  used  in  the 
rough,  but  should  not  exceed  an  inch  in  butt  diameter  for  gabions 
and  hurdles  and  2.5  in.  for  fascines  and  pickets. 

The  working  party  cuts  and  binds  the  brushwood  in  bundles  of 
about  40  lbs.  caili.  putting  the  large  and  small  in  separate  piles 
with  butts  in  the  same  direction.  For  convenience,  the  detail 
should  be  divided  into  three  parts — one  for  cutting,  one  for  sort- 
ing and  binding,  the  other  for  carrying  and,  if  necessary,  loading. 
Tools  required  and  time  necessary  are  as  in  "Clearing  the  Ground" 
(Chap.  V). 

116. — Witlies  (PI.  17,  Fig.  1).  which  are  used  for  binding  and 
sewing,  are  made  by  twisting  a  pliant  rod.  The  butt  is  held  under 
the  left  loot  and  tlie  twisting  commenced  at  the  small  end,  care 
being  taken  to  avcnd  breaking  or  kinking  the  rod.  The  pliancy  of 
the  rod  may  be  increased  by  heating  it.  In  using  the  withes  for 
binding,  an  eye  is  made  at  the  small  end,  then  the  withe  is  passed 
round  the  bundle,  the  butt  passed  through  the  eye  and  twisted 
until  a  kink  is  formed,  when  the  butt  is  thrust  (buried)  in  the 
bundle. 

117. — Fascines.  A  fascine  is  a  bundle  of  rods  tightly  bound 
together.  It  has  a  length  of  18  ft.,  a  diameter  of  9  in.,  and  weighs 
about  140  lbs. 


PLATE  17 


.     np.8. 


Revetting  Materials  and  Revetments.  77 

Fascine  Rack. — The  fascine  is  made  in  a  cradle  rack  of  five 
equidistant  trestles  (Figs.  2  and  4),  the  outer  ones  being  16  ft. 
apart,  the  crotches  are  each 2.5  ft.  above  the  ground  and  aligned.  The 
stakes  for  the  trestles  should  be  from  2.5  to  4  in.  in  diameter  and 
from  5  to  6  ft.  in  length.  Those  for  the  outer  trestles  are  first 
driven  and  securely  bound  together  with  wire  or  rope,  then  a  line 
is  stretched  from  crotch  to  crotch  and  the  interior  trestles  made 
in  a  similar  manner  :  the  stakes  should  be  driven  firmly  into  the 
ground  and  each  should  have  a  length  of  2  ft.  above  the  crotch. 

Fascine  Clioker. — For  the  purpose  of  gauging  the  circum- 
ference of  the  fascine  and  for  cramping  it  in  binding,  the  fascine 
choker  (Fig.  3)  is  used.  It  consists  of  two  stout  bars  or  hand- 
spikes, 4  ft.  long,  to  each  of  which  is  attached  a  collar  18  in.  from 
the  end,  the  collars  being  connected  by  a  stout  chain,  to  which 
are  attached  two  gauge  links  28  in.  apart.  The  choker  is  used  by 
a  man  on  each  side  of  the  rack  taking  a  bar  of  it  and  resting  the 
short  end  on  top  of  the  fascine,  chain  being  underneath  (Fig.  4, 
"a");  then  each  passes  his  bar  over  to  the  other  (the  short  ends 
passing  around  and  under  the  fascine),  and  each  bears  down  on 
the  end  of  his  lever.     (Fig.  4,  "b.") 

Making"  tlie  Fascine. — The  trestles  having  been  prepared, 
the  fascine  is  made  by  laying  brushwood,  trimmed  if  practicable, 
in  them,  the  pieces  breaking  joints  and  crooked  ones  being  partly 
sawed  or  cut  through.  The  rods  should  extend  from  18  in.  to  2  ft. 
beyond  the  extreme  trestles  and  the  bunch  made  of  uniform  size 
throughout.     (Fig.  4.) 

The  choker  should  be  used  occasionally  for  testing  the  size  and 
when  of  such  dimensions  throughout  that  the  gauge  rings  meet,  the 
fascine  is  bound.  This  should  be  done  with  wire  or  tarred  rope, 
which  is  passed  twice  round  the  fascine  and  securely  fastened,  the 
bindings  being  12  in  number,  the  two  outer  ones  3  in.  outside  the 
extreme  trestles  and  the  others  at  intervals  of  about  a  foot  and  a 
half.  This  allows  the  fascine  to  be  cut  into  lengths  of  6  or  of  9 
ft.     Five  men  require  about  an  hour  to  make  a  fascine. 

118. — Gabions.  Gabions  are  open  cylinders  2  ft.  in  exterior 
diameter  by  2  ft.  9  in.  in  height,  varying  in  weight  from  35  to  50 
lbs.:  they  are  made  of  bj'uslnrood,  ntvap  iron,  iron  hands  or  sheet 
iron  and  from  9  to  14  pickets  each.  The  interlaced  brushwood  in 
gal)ions  is  called  the  watling  or  web.  Gabion  pickets  should  be 
3.5  ft.  in  length  and  from  an  inch  to  an  inch  and  a  half  in  diame- 


78  Revetting  Materials  and  Revetments. 

ter.  The  rods  for  the'web  should  be  from  one-lialf  to  three-fourths 
of  an  inch  in  diameter,  although  smaller  may  be  lased.  Wicker 
gabions  are  most  easily  made  with  the  aid  of  a  gabion  form,  which 
is  a  circular  piece  of  board  21  in.  in  diameter,  with  equidistant 
notches  on  its  circumference,  the  number  of  notches  depending 
on  the  size  of  the  brushwood  and  running  from  9  to  14.  (Fig.  5.) 
The  construction  of  the  Wicker  Gabion  (Fig.  7)  is  as  follows : 
Wailing.  The  gabion  form  is  laid  on  level  ground  and  a 
picket  driven  vertically  in  each  notch,  the  thick  and  thin  ends 
of  the  pickets  alternating.  The  form  is  thenslijjped  up  the  pickets 
about  a  foot  and  held  firmly  in  place  by  means  of  a  rope  which  is 
tied  l(K>sely  round  the  jiickets  just  below  the  form  and  then  tight- 
ened by  a  rack  stick  (Fig.  6),  the  rope  holding  the  pickets  firmly 
in  the  notches.  The  rods  for  the  web  having  been  stripped  of 
their  leaves,  the  web  is  commenced  by  laying  the  butts  of  two  rods 
in  adjacent  spaces  between  pickets,  resting  on  the  form.  The  rear 
rod,  passing  outside  the  second  picket,  is  then  bent  inward,  pass- 
ing over  the  first  rod,  inside  the  third  picket,  and  then  out.  (Fig. 
T). )  The  other  rod,  which  is  now  the  rear  one,  is  similarly  treated 
and  the  watling  continued  by  using  the  rods  alternately.  This 
method  of  watling  is  called  pairing.  On  coming  to  the  end  of  a 
rod  a  fresh  one  is  laid  alongside  and  woven  with  it  for  a  short  dis- 
tance. The  web  is  continued  to  within  3  in.  of  the  ends  of  the 
pickets,  care  being  taken  to  keep  the  pickets  vertical  and  to  make 
the  web  close  by  frequent  use  of  the  mallet. 

Sewing*.  To  prevent  the  web  from  coming  off  the  pickets  it  is 
then  sewed  with  wire,  heavy  twine,  or  withes,  in  four  places,  as 
follows:  Take  an  end  of  a  withe  in  each  hand,  the  middle  of  it 
resting  on  the  web,  pass  the  ends  of  it  through  the  wel^  about  6 
in.  down  the  sides,  one  from  without  inw aid  and  the  other  from 
within  outward ;  pull  taut  by  bearing  downward.  Pass  the  ends 
through  the  web  again  G  in.  farther  down  and  tighten  as  before. 
Proceed  in  the  same  manner  a  third  time  and  then  bury  the  ends 
of  the  withe  in  the  web.  The  sewing  should  be  at  equal  inter- 
vals and  the  two  ends  of  the  withe,  when  pushed  through  the 
web,  should  be  separated  by  two  or  three  of  the  watling  rods; 
wire  is  much  easier  worked  and  more  durable  than  withes.  The 
partly  completed  gabion  is  now  inverted,  the  form  removed,  and 
the  watling  continued  as  before,  until  the  gabion  has  a  height 
of  2  ft.  9  in.,  when  it  is  completed  by  again  sewing  as  before  ex- 


Revetting  Materials  and  Revetments.  79 

plained.  The  ends  of  the  pickets  that  were  driven  into  the 
ground  are  now  trimmed  to  within  3  in.  of  the  web  and  sharp- 
ened, the  opposite  ends  sawed  off  to  within  an  inch  of  the  web, 
and  a  carrying  picket  driven  through  the  sides  of  the  gabion  per- 
pendicular to  the  axis  and  a  few  inches  from  it. 

Three  men  should  make  a  gabion  in  an  hour. 

119. — Wicker  Gabion  Witlioiit  tlie  Gabion  Form. 
Where  the  form  is  not  at  hand  the  wicker  gabion  is  made  by 
first  describing  on  the  ground  a  circle  with  a  10.5  in.  radius  and 
then  driving  the  pickets  at  equidistant  intervals  on  this  line. 
The  watling  is  commenced  at  the  ground  and  run  up  to  the  full 
height,  care  being  taken  by  frequent  gauging  to  keep  the  dimen- 
sions accurate.  It  will  be  necessary  for  one  man  to  devote  his 
entire  attention  to  keeping  the  pickets  in  position,  while  a  second 
makes  the  web,  and  a  third  prepares  the  rods.  Three  men  should 
make  a  gabion,  without  the  form,  in  an  hour  and  a  half  to  two 
hours.  Instead  of  sewing,  the  gabion  may  be  finished  by  driving 
four  forked  pickets  (Fig.  8)  in  the  web  alongside  of  the  gabion 
pickets. 

120. — Tlie  Hoop  or  Straj^  Iron  Gabion.  This  is  more 
durable  and  more  quickly  made  than  the  wicker  gabion,  but  is 
heavy,  weighing  55  lbs.,  and  liable  to  splinter  dangerously.  The 
form  for  this  gabion  is  used  solely  for  gauging  and  shaping  the 
bands. 

To  make  tlie  liooi^s,  describe  on  a  wooden  platform  a  cir- 
cle with  a  1  ft.  radius  and  divide  it  into  6  equal  parts.  Make 
auger  holes  at  points  of  division  and  insert  in  them  wooden  pins 
about  5  in.  long  and  triangular  in  cross  section,  the  bases  of  the 
triangles  being  on  the  interior  of  the  circle.  (Fig.  9.)  Wrap  the 
strap  iron  once  tightly  round  the  pins,  thus  forming  an  hexagonal 
hoop.  Mark  the  point  where  the  hoop  is  to  be  joined,  then  re- 
move, punch,  and  rivet  it.  As  the  iron  is  usually  1  in.  wide  the 
completed  gabion  will  require  33  of  these  hoops. 

To  make  tlie  gabion,  place  a  hoop  on  the  ground  and  an- 
other on  it  in  the  positions  shown.  (Fig.  10.)  Drive  a  picket 
vertically  in  each  of  the  triangular  spaces,  then  place  the  remain- 
ing hoops  alternately  over  the  first  and  second.  Drive  nails  in 
four  of  the  pickets  outside  the  extreme  hoops  to  keep  the  gabion 
intact. 


80  Revetting  Materials  and  Revetments. 

1 21 .— Tlie  Sheet  Iron  Gabion.  This  gabion  is  made  of  a 
piece  of  sheet  iron  2  ft.  9  in.  x  G  ft.  4  in.,  riveted  or  wired  together 
along  its  shorter  edges. 

122.— Hurdles.  The  hurdle  is  a  brushwood  mat  2  ft.  9  in. 
wide  by  6  ft.  long,  the  length  corresponding  very  nearly  to  the  cir- 
cumference of  the  gabion.  An  even  number  of  pickets,  usually 
10,  is  used  in  making  it,  the  extreme  pickets  being  somewhat 
heavier  than  the  interior  ones.     (Fig.  11.) 

Construction  of  Hurdles.  Describe  on  the  ground  an  arc 
with  an  8  ft.  radius,  measure  off  6  ft.  of  this  arc  and  drive  10 
gabion  pickets  along  it  at  intervals  of  8  in.  (Fig.  11.)  Commence 
the  watlftig  in  the  center  space  on  the  ground  by  randing,  i.  e. 
working  with  a  single  rod  alternately  inside  and  outside  of  the 
pickets ;  on  reaching  the  end  picket  the  rod  should  be  twisted  as 
a  withe,  so  as  to  avoid  breaking  it,  and  then  returned  toward  the 
center  in  the  same  manner  as  at  tirst.  When  approaching  the 
end  of  a  rod  another  should  be  laid  alongside  of  and  randed  with 
it  for  a  distance  of  two  or  three  pickets.  Pairing,  as  in  gabions, 
should  be  resorted  to  in  finishing  the  top  and  bottom  of  the  web 
and  the  hurdle  should  then  be  sewed  as  described  for  the  gabion. 
When  the  rods  used  in  watling  are  very  small  the  process  of  slew- 
ing should  be  resorted  to:  this  is  the  same  as  randing  with  the 
exception  that  2  or  3  rods  are  laid  alongside  each  other  instead  of 
using  them  singly.  Slewing  makes  weaker  work  than  randing. 
Three  men  should  make  a  hurdle  in  two  hours;  two  work  at  the 
w^eb  and  the  third  prepares  the  rods.  The  completed  hurdle 
weighs  about  50  lbs.  The  hurdle  is  made  on  a  curve  and  after- 
ward flattened  as  much  as  possible,  because  it  is  found  that  by 
so  doing  it  is  less  liable  to  warp  than  if  made  flat.  It  should  be 
I^laced  in  a  road  or  revetment  with  the  concave  side  toward 
the  earth. 

123. — Tlie  C\)iitiniioiis  Hurdle  is  usually  preferred  for 
revetting  jjurposes  to  single  ones  joined.  It  differs  from  the 
latter  in  that  the  pickets  are  driven  at  once,  at  intervals  of  12  to 
18  in.  according  to  their  thickness,  in  the  position  the  revetment 
is  to  occupy,  but  at  a  slightly  gentler  slope  so  as  to  allow  for 
straightening  when  the  earth  is  tamped.  It  is  constructed  by 
randing  or  slewing,  two  men  being  assigned  a  task  of  10  or  12  ft. 
in  length,  which  they  should  finish  to  a  height  of  4  ft.  and  anchor, 
in  from  one-half  to  three-quarters  of  an  hour. 


PLATE  18. 


Revetments. 


I  liii 


,j^^fh^mf^%w^^'mWMw--^n^^i 


Revettinc;  Materials  and  Revetments.  83 

124. — Planks  when  used  for  revetting  should  be  placed 
edgewise  and  held  in  position  by  stout  stakes  which  should  be 
anchored.  They  make  a  neat,  durable  and  quickly  made  revet- 
ment. 

125. — Roiiiid  timber  from  3  to  8  in.  in  diameter  may  be 
used  in  the  same  manner  as  planks  but  the  revetment  is  more 
difficult  of  construction  and  is  not  so  durable. 

126.— Sod  for  revetting  purposes  is  cut  of  a  uniform  size — 18 
in.  long,  9  in.  wide,  and  4  in.  thick.  They  should  be  laid  in  alter- 
nate rows  of  headers  and  stretchers,  grass  down,  breaking  joints, 
and  perpendicular  to  the  slope.  The  top  layer  should  be  all  head- 
ers and  have  the  grass  up;  alternate  rows  should  be  pinned 
securely,  using  split  pickets,  if  possible,  as  with  them  there  is  less 
liability  of  splitting  the  sod  than  when  round  ones  are  used. 
Two  men  should  lay  from  70  to  100  sods  per  hour,  depending 
upon  whether  or  not  pickets  are  used. 

127. — Sand-bags  are  made  of  coarse  canvas  or  bagging 
material  and,  when  empty,  measure  2  ft.  8  in.  by  1  ft.  4  in.  When 
tilled  they  are  supposed  to  contain  1  cubic  ft.  of  earth ;  it  is  found 
in  practice,  however,  that  a  cubic  yard  will  fill  from  48  to  50, 
making  their  average  size  1  ft.  6  in.  long,  10  in.  wide,  and 
6  in.  thick.  Each  bag  has  eyelet  holes  near  the  mouth  through 
which  a  stout  cord  passes,  to  expedite  tying,  when  filled. 

For  filling  sand-bags  the  working  party  is  divided  into  squads 
of  6 :  2  with  shovels,  1  with  a  pick,  1  to  hold  the  bag,  and  2  to  tie. 

Each  squad  fills  150  bags  per  hour.  This  task  may  be  consid- 
erably increased,  however,  in  easy  soil  or  with  trained  men,  and 
the  rapidity  of  the  work  more  than  doubled  by  having  a  double 
relief  and  keeping  the  men  constantly  changing. 

128. — Revetments.  Brushwood  Revetment  is  made 
by  driving  pickets  at  intervals  of  about  12  in.  along  the  foot  of 
the  proposed  slope.  The  top  of  the  pickets  when  driven  should 
be  as  high  as  the  proposed  revetment,  and  the  pickets  should  be 
anchored  by  wire  to  logs  or  stout  stakes  in  the  parapet.  Loose 
brushwood  is  laid  closely  behind  the  stakes  and  earth  tamped 
against  it,  the  construction  of  the  parapet  going  on  at  the  same 
time- 
Brushwood  revetment  is  rapidly  made  in  daylight  but  is  neither 
durable  nor  sightly. 

129.-  Tlie  Fascine  Revetment.     (PL  18,  Fig.  1.)    This  is 


H4  I V  i  ;\  KTTl  N( .   MATKlil  A  LS  AiN  1)  KkVKTMKiNTS. 

lujulc  l)\  la\  iii<j^  the  fascines  in  single  rows  of  stretchers,  breaking 
joints,  each  fascine  being  x^inned  to  the  parapet  by  5  or  6  pickets, 
and  every  second  or  third  row  securely  anchored. 

Six-foot  fascines  should  be  used  occasionally  as  headers.  The 
bottom  fascine  is  sunk  about  one-third  of  its  diameter  by  excavat- 
ing a  shallow  trench.  The  construction  of  parapet  and  revetment 
proceed  simultaneously.  Slope  should  not  be  greater  than  four 
on  one.  The  defects  of  this  revetment  are  the  weight  of  the 
facines,  the  large  quantity  of  brushwood  required,  and  llic  fact 
that  the  fascines  are  held  in  place  by  anchors  and  pickets  in  the 
earth  which  they  support. 

130.  Tlie  Gabion  Ilevetmeiit.  (Fig.  2.)  This  is  made 
by  first  sinking  a  row  of  fascines  about  3  in.  at  the  foot  of  the 
elope,  so  as  to  give  an  inclination  of  four  on  one  to  the  gabions 
resting  i^artially  on  them.  Earth  is  tamped  behind  and  in  tha 
gabions,  and  sod  or  sand-bags  placed  on  top.  Where  greater 
height  is  required  two  rows  of  gabions  may  be  used  with  two 
facines,  well  picketed,  between  them. 

Gabions  make  one  of  the  strongest  and  most  durable  revet- 
iiKMits.  11i(  ii-  own  weight  when  filled  being  usually  sufficient  to 
I'l^tain  t  Ih' einl)ankment. 

MM,  I  111  relies.  These  make  a  poor  revetment  unless  the 
method  is  followed  of  constructing  a  ^^continuoitH  hurdle''  at  the 
same  time  with  the  parapet.  To  do  this,  the  pickets  are  driven 
along  the  foot  of  the  slope  at  an  inclination  of  about  three  on 
one,  when  the  final  slope  is  to  be  four  on  one.  The  watling  is 
made  continuous  by  randing  or  slewing,  each  two  men  having 
four  paces  of  hurdle  as  a  task,  and  taking  care  to  work  in  their 
rods  with  those  of  adjacent  sections.     (Fig.  3.) 

132.— Plank  or  Timber  Revetment.  (Fig.  4.)  This  is 
made  by  driving  heavy  stakes  into  the  ground  at  the  proper  angle, 
placing  the  planks  or  timbers  behind  them,  then  filling  in  and 
tamping  firmly.  The  stakes  must  be  anchored.  This  revetment 
is  neat  and  durable. 

133."Sod  llevetmcnt.  (Fig.  5.)  This  is  made  by  laying 
the  sod  in  alternate  layers  of  headers  and  stretchers,  grassy  side 
down,  breaking  joints  and  perpendicular  to  the  face  of  the  revet- 
ment. Each  sod  should  be  well  settled  before  another  is  placed 
on  it  and  the  top  layer  should  be  headers  w^ith  grass  up.  It  is 
well    to  pin  alternate  rows  by    means  of    split   pickets,   three 


Revetting  Materials  AND  Revetments.  I   ^'^^r 

lourths  of  an  inch  in  diameter  and  9  in.  long.  This  revetme^ 
made  of  uniform  thickness  throughout  by  using  double  rows^ 
stretchers.  If  the  grass  is  long  it  should  be  mowed.  If  the  sod 
is  very  wet  when  laid  the  revetment  will  crack  in  drying.  Two 
men  well  supplied  with  sod  should  lay  two  paces  of  revetment,  four 
and  one-third  feet  high,  in  an  hour. 

This  revetment  has  the  advantage  of  not  splintering  like 
gabions,  fascines  and  boards,  but  should  not  be  used  when  other 
material  is  obtainable  because  ordinarily  it  will  not  stand  long  at 
a  steep  slope  (three  on  one  being  about  the  limit),  cannot  be  used 
when  very  dry  or  frozen,  and  requires  great  care  to  build  prop- 
erly. 

134.— Saiid-bag  Revetment.  (Fig.  6.)  This  is  made  by 
laying  alternate  rows  of  headers  and  stretchers,  breaking  joints, 
and  perpendicular  to  slope,  seams  of  stretchers  and  chokes  of 
headers  being  put  in  the  embankment.  Men  working  in  pairs 
lay  the  bags,  settling  them  firmly  in  place  with  a  mallet  or  spade. 
This  revetment  is  not  very  durable  but  the  bags  are  easily  trans- 
ported, may  be  used  with  any  soil,  and  are  invaluable  in  making 
hasty  repairs  and  loop-holes. 

135. — A  very  durable  revetment,  (Fig.  7,)  much  used  in  the 
defences  of  Washington  1861-5,  was  made  of  posts  (oak,  chestnut, 
or  cedar)  cut  in  lengths  of  5.5  ft.  and  placed  side  by  side,  at  a 
slope  of  six  on  one.  The  footing  was  a  2  in.  plank  laid  in  a  trench 
excavated  for  the  purpose.  The  tops  of  the  posts  were  sawed  off 
16  in.  below  the  inferior  crest  and  capped  by  a  half-round  timber, 
all  being  securely  anchored  in  the  parapet.  Crowning  was  com- 
pleted to  the  requisite  height  with  sod. 

All  revetments  that  are  liable  to  splinter  should  be  crowned  to 
a  height  of  at  least  8  in.  with  sods,  sand-bags  or  earth. 

136. — Pisa  Revetment  is  made  of  earth  and  clay,  to  which 
has  been  added  enough  water  to  reduce  the  mixture  to  a  working 
consistency.  A  trench  6  in.  deep  and  18  in.  wide,  is  first  dug,  its 
nearest  edge  marking  the  foot  of  the  revetment.  Pickets,  of 
sufficient  length  to  reach  the  top  of  the  proposed  revetment,  are 
firmly  driven,  at  the  proper  angle,  about  2  in.  from  the  near  edge 
of  the  trench,  at  intervals  of  about  a  yard,  and  then  anchored. 
Boards  placed  horizontally  are  now  laid  against  the  pickets  on 
the  trench  side.  The  trench  is  then  filled  with  the  mixture, 
tamped,  and  more  added,  other  boards  being  placed  on  top  of  the 


8(5 


Revetting  Matekials  and  Revetments. 


first,  as  required,  and  the  mixture  forced  closely  against  them 
The  construction  of  the  parapet  goes  on  at  the  same  time  with 
the  revetment.  When  completed,  the  pickets  and  boards  are 
removed,  This  revetment  is  neat  and  durable  but  cannot  be 
rapidly  made. 

137. — Tlie  Adobe  is  a  sun-dried  brick,  about  18  in.  x  9  in.  x 
4.5  in.  and  when  carefully  laid  with  the  same  bond  as  given  for 
sod  or  sand-bag,  forms  a  neat  and  very  durable  revetment,  exceed- 
ing in  the  latter  respect  any  of  the  other  varieties  mentioned. 

The  following  table  shows  amount  of  various  materials  required 
for  100  running  ft.  of  4  ft.  4  in.  high  revetment. 


Kind  of  Revetment 

Fascines 

Gabions 

Sod 

Sand- bags 

Pickets 

Facines 

Gabion 

Sod 

30 

G 

50 

26t" 
400 
1867 

867 

150 

1000 

Sand-bag 

PLATK  19. 


Field  Casemates. 


ClIAPTKK  X.— Field  Casemates  and  Ma^^aziiies. 


138. — In  all  field  works,  protection  against  both  weather  and 
hostile  fire  must  be  provided  for  the  garrison. 

These  shelters  are  constructed  by  building  a  chamber  of  wood 
sufficiently  strong  to  bear  the  necessary  earth  covering,  and  by 
protecting  this  in  front  by  an  embankment  thick  enough  to  with- 
stand direct  artillery  fire. 

Two  general  forms  are  used : — 

(1)  Those  which,  after  providing  complete  protection  from  di- 
rect fire,  have  their  roofs  sloped  to  the  rear  at  an  angle  greater 
than  the  angle  of  descent  of  the  enemy's  projectiles,  generally 
about  one  on  four  ;  and, 

(2)  Those  which  have  horizontal  roofs,  the  earth  covering  being 
so  high  and  massive  as  to  protect  against  artillery  fire  by  its  thick- 
ness alone. 

The  first  class  is  preferable,  the  work  of  construction  being 
very  much  less  than  in  the  second  class,  as  the  embankment  is 
not  so  high  and  the  earth  on  the  roof  does  not  require  to  be 
thicker  than  16  in.,  as  it  has  to  resist  only  the  dropping  fire  of 
small  arms  and  the  fragments  from  bursting  shrapnel.  More- 
over, it  gives  much  easier  drainage  to  the  ditch  in  rear. 

139. — The  construction  of  the  timber  part  of  the  casemate  is 
practically  the  same  in  both  cases.  The  vertical  timbers  being 
rough  tree  trunks,  about  1  ft.  in  diameter,  placed  at  intervals  of 
3  or  1  ft.,  and  strutted  when  necessary.  The  roof  timbers  in  sim- 
ple casemates  being  not  less  than  8  in.  in  diameter  and  the  inter- 
stices filled  with  small  poles  or  brush.  In  case  the  protection  has 
to  be  proof  against  vertical  fire  of  mortars,  the  earth  mask  on  the 
roof  must  be  6  ft.  in  thickness  and  a  correspondingly  stronger 
timber  construction  must  be  provided :  these  are  shown  in  PL  19, 
Figs.  1  to  7. 


W  Field  Casemates  and  Macjazines. 

In  calculating  floor  space,  each  man  should  have  from  9  to  18 
sq.  ft.;  the  former  when  crowded,  the  latter  when  not. 

140. — Ma<^aziiies  are  of  two  kinds :  Fh^st,  those  intended  to 
hold  the  temporary  supply  for  guns  or  troops  when  in  action; 
and,  Second,  those  intended  for  the  purpose  of  storing  ammuni- 
tion in  large  quantities. 

The  first  variety  consists  of  recesses  in  the  interior  slope  of  the 
epaulement — barrels  or  gabions  are  excellent  and  when  not  ob- 
tainable may  be  replaced  by  empty  ammunition  boxes  placed  in 
holes  excavated  for  their  reception. 

Magazines  of  the  second  class  are  used  only  in  w^orks  of  great 
defensive  value  and  then  only  when  ample  time  is  available. 
They  are  made  in  the  same  general  manner  as  the  casemates 
heretofore  described,  except  that  great  care  must  be  taken  to 
render  the  structure  as  dry  as  possible  and  to  secure  good  venti- 
lation. 

141. — The  general  plan  of  execution  of  these  works  is  as 
follows  :— 

(1)  Magazine  shown  in  PI.  20,  Fig.  1. 

The  mask  in  front  should  be  20  ft.  thick.  The  roof  consists  of 
a  row  of  timbers  or  logs  8  in.  in  diameter,  overlaid  with  steel  rails, 
and  then  covered  with  a  paulin,  well  tarred  if  possible.  On  this 
is  placed  IG  to  18  in.  of  earth.  The  ends  are  made  of  logs,  12  in. 
in  diameter,  planted  in  a  double  row,  breaking  joints.  The  en- 
trance is  at  either  one  or  both  ends  according  to  circumstances. 
The  doors,  2  ft.  6  in.  in  width,  are  made  of  planks  crossed,  and  are 
hung  next  to  the  front  wall  of  trench,  opening  into  a  passage 
formed  by  a  row  of  upright  logs  parallel  to  those  on  the  end  of 
the  magazine.  At  the  end  of  the  passage  farthest  from  the  first 
door  a  second  one  is  hung,  opening  into  the  magazine.  The 
vertical  timbers  in  front  and  rear  of  trench  support  a  revetment 
of  planks  or  hurdles.  The  floor  should  be  raised  at  least  6  in. 
from  the  bottom  of  the  trench,  to  guard  against  dampness. 
Care  should  be  taken  to  facilitate  the  draining  of  all  water  that 
falls  on  the  roof,  and  that  the  trench  itself  is  drained  away  from 
the  ends  of  the  magazine. 

142.  — Another  form  is  as  follows :  — Determine  the  space 
needed  for  storage  of  ammunition.  Then  build  the  timber  work 
as  in  the  preceding,  first  excavating  to  a  depth  of  4  or  5  ft.  over 
the  entire  site.     There  will  be  no  ends  to  be  closed  by  timbers. 


PLATE  20. 


Maprazine  behind  naranet. 


Tu/o  Storlecl  Block IIouso. 

Caponier  tn  front  ofwalL 


Field  Casemates  and  Magazines.  93 

The  roof  is  made  of  timbers  12  in.  in  diameter,  well  supported  by 
uprights  of  same  size  and  long  enough  to  give  sufficient  head 
room.  The  sides  and  ends  should  be  revetted  with  plank,  if  pos- 
sible, and  the  floor  raised  6  in.  above  the  earth.  The  center  of 
the  roof  is  raised  a  foot  above  the  sides  and  surmounted  by  a 
layer  of  6  in.  of  earth,  well  tamped ;  over  this  is  laid  a  paulin  and 
the  earth  mask  is  then  placed  over  all  to  the  thickness  of  8  ft.; 
the  covering  mass  in  front  should  not  be  less  than  20  ft.  in  thick- 
ness. Entrance  is  gained  by  means  of  a  doorway  opening  into  a 
passage  which  communicates  through  a  return  with  the  interior 
of  the  magazine.  Doors  made  of  crossed  planks  are  hung  as  in- 
dicated in  the  plan.  If  time  is  available,  and  the  planks  at  hand, 
an  interior  chamber  should  be  formed,  leaving  an  air  space 
around  the  magazine  proper ;  and  inlets  may  be  constructed,  care 
being  taken  that  they  are  not  situated  in  e:^posed  positions  and 
that  their  course  is  such  as  to  prevent  the  entrance  of  sparks. 
The  roof  should  be  rounded  off  so  as  to  afford  the  easiest  drain- 
age. If  the  earth  excavated  is  not  sufficient  to  cover  the  roof,  the 
necessary  amount  may  be  taken  from  a  trench  dug  around  the 
outside. 

This  form  of  magazine  may  with  advantage  be  placed  in  a 
traverse. 

143. — 111  case  timber  is  not  at  liaiid,  gabions  and  fas- 
cines may  be  used  to  build  the  magazine  in  the  manner  shown  in 
PI.  20. 

144. — Block  Houses  are  defensible  shelters  for  infantry, 
although,  under  certain  circumstances,  they  contain  artillery. 

They  are  generally  used  for  the  purpose  of  flanking  defenses 
whose  fire  cannot  reach  into  the  ditch. 

They  are  constructed  either  of  upright  timbers  set  in  the 
ground  close  together,  or  horizontal  timbers  laid  one  upon  the 
other;  the  timbers  being  in  two  rows,  breaking  joints  in  each 
case,  or,  if  both  methods  are  used,  the  outside  row  should  be  hori- 
zontal and  the  inner  vertical.  They  should  have  at  least  6  ft.  of 
head  room  and  should  not  be  less  than  9  ft.  wide,  as  this  allows 
one  row  of  beds  only.  The  roof  should  be  of  solid  construction 
and  covered  with  earth  to  the  thickness  of  2  ft.  and  should  pro- 
ject 2  ft.  over  the  wall  to  protect  from  dropping  fire. 

The  walls  should  be  masked  with  earth  as  high  as  possible  and 
a  ditch  dug  around  the  entire  building.    Loop  holes  are  made  at 


94  Field  Casemates  and  Magazines. 

the  height  of  4  ft.  4  in.  and  are  cut  according  to  circumstances, 
as  described  in  Chap.  XIII.  If  necessary,  block  houses  may  be 
sunk  in  the  ground,  but  a  limit  of  4  ft.  in  depth  should  be  ob- 
served.   The  shape  will  conform  to  the  necessities  of  the  case. 

145. — 111  isolated  positions  they  are  advantageously  made 
cruciform,  thus  presenting  an  opportunity  for  flanking  each  face 
of  the  house.  When  in  wooded  and  mountainous  countries, 
where  artillery  is  not  to  be  feared,  these  houses  may  be  made 
with  two  stories,  built  so  that  the  angles  of  the  upper  story  pro- 
ject over  the  sides  of  the  other,  forming  a  machicoulis  gallery, 
thus  preventing  the  occupation  by  the  enemy  of  the  dead  space 
in  front  of  the  straight  walls. 

146. — Cajioiiiers  are  sunken  block  houses  placed  in  the 
ditch  of  fortified  places  to  prevent  their  occupation  by  the  enemy: 
they  are  loop-holed  about  18  in.  from  the  ground,  so  as  to  have  the 
most  effective  plane  of  fire.    (PI.  20.) 

147.— Tambours  are  essentially  block  houses,  having  for 
their  object  the  protection  of  angles,  and  the  flanking  of  sides  of 
buildings,  and  are  especially  useful  in  defending  doors  of  build- 
ings. 


CHAPTER  XI.— Field  Works  in  Combination. 


148. — Where  several  field  works  are  used  in  conjunction, 
either  as  an  intrenched  position  or  in  the  investment  of  a  fortress, 
city,  or  other  important  point,  they  constitute  what  is  known  as  a 
Line  of  Woy^ks. 

A  liine  of  Works  may  be  continuous,  that  is,  forming, 
together  with  natural  obstacles,  an  unbroken  line,  or,  with  inter- 
vals, by  which  it  is  understood  that  the  works  are  distinct, 
either  suijporting  each  other  or  not,  and  the  spaces  between 
them  not  impassable  by  reason  of  natural  obstacles. 

149. — Ijines  witli  intervals  have  the  following  advantages 
over  continuous  lines,  viz: — 

(a)  They  involve  less  labor. 

(b)  The  garrison  of  the  defenders  may  be  smaller. 

(c)  They  allow  greater  freedom  of  movement  for  counter  attacks. 

The  general  principle  to  be  followed  in  their  construction  con- 
sists in  forming  a  line  of  fortified  points  or  pivots.  These  points 
or  pivots  detain  the  enemy's  advance,  since  he  would  hardly  pass 
them  and  expose  his  flanks  and  rear,  while  a  continued  unsuc- 
cessful attack  on  the  strongly  fortified  pivots  would  open  the  way 
for  a  counter  attack  by  the  defenders. 

When,  however,  the  defense  is  intended  to  be  solely  passive, 
which  would  be  the  case  while  awaiting  reinforcements,  or  when 
the  enemy  greatly  outnumbers  the  defenders,  the  intervals  would 
be  obstructed  by  felling  trees  or  using  any  available  obstacles, 
since  counter  attack  is  not  contemplated. 

In  the  use  of  lines  with  intervals,  if  the  general  defensive  line 
is  straight  the  w^orks  could  be  blunted  lunettes  with  flanks  traced 
so  as  to  protect  the  front  of  adjacent  works.  If  on  a  convex 
curve,  'the  capitals  should  radiate  from  a  common  center,  while 


l>0  Field  Works  in  Combination. 

on  a  curve  concave  toward  the  enemy,  the  capitals  should  con- 
verge and  the  front  of  each  work  might  be  a  straight  line. 

When  impracticable  to  construct  the  main  works  of  a  line  with 
intervals,  within  supporting  distance  (600  yds.  for  infantry  and 
2000  yds.  for  artillery)*  of  each  other,  intermediate  works  retired 
from  the  main  line,  not  more  than  half  the  interval,  may  be 
used. 

In  PI.  21,  Fig.  6.  is  shown  such  an  arrangement,  the  pivots 
being  single  works  while  the  artillery  is  retired  from  the  main 
line  and  supported  by  infantry  in  shelter  trenches. 

Where  the  interval  is  as  great  as  1,500  yds.  it  is  advisable  to 
strengthen  the  pivots  considerably,  forming  groups,  the  individ- 
ual works  of  each  group  being  so  traced  as  to  afford  mutual 
defense.  ( PI.  15,  Fig.  2.)  Each  group  in  this  latter  arrangement 
forms  a  strongly  fortified  point  of  support  and  would  usually  have 
suflScient  strength  in  itself  to  resist  assault. 

150. — Sometimes,  when  the  defense  of  a  line  is  of  vital  impor- 
tance to  the  defenders,  a  douhlr  line  of  trorks  is  employed,  the 
front  line  being  shelter  trenches  or  open  field  works  of  slii!:ht 
profile,  the  second  line,  not  over  500  yds.  in  rear  of  the  first,  ])eing 
field  works  of  strong  profile. 

151. — Artillery  should,  as  a  rule,  be  placed  outside  of  and 
somewhat  retired  from  the  works  and  protected  by  their  own  gun- 
pits  or  epaulements,  for  the  reasons — 

(1)  That  the  works  gain  much  in  simplicity  and  rapidity  of 
construction. 

(2)  That  this  disposition  drawls  the  enemy's  artillery  fire  from 
the  works  and  renders  it  more  scattering. 

(3)  Greater  mobility  is  given  to  the  defender's  artillery  in  case 
of  advance  or  retreat. 

(4)  A  better  tactical  position  for  this  arm  can  often  be  secured 
than  the  one  selected  for  infantry. 

152. — As  examples  of  continuous  lines,  PI.  21,  Fig.  1.  is  known 
as  the  redan  trace  with  curtains.  Fig.  2.  is  a  modification  of 
Fig.  1.,  the  redans  being  blunted.  Fig.  3.  is  the  tenaille  trace. 
Fig.  4.  is  a  tenaille  and  redan  trace.  The  cremaillere  trace  (Fig.  5) 
has  long  faces  and  short  flanks. 

With  respect  to    the    continuous  lines  above  mentioned,  the 


*  Continuous  dangerous  spac©  for  new  Infantry  rifle  (Krag-Jorgenson)  is  610  yards. 


PLATE  21. 


PIG.l. 
i30  to  600  mtxif  /^toeoy,^,^^ 

FIG.2, 


FIG.5. 


, ^    6WtoiZ00<^rds 


FIG.6. 


•^^^^^ 


Ji^ilitary  Ovst 
FIG.  7  :  6 


Field  Wokks  in  Comiunatjon.  99 

preference  on  a  level  site  would  usually  be  given  to  the  trace 
shown  in  Figs.  1  and  2,  the  artillery  being  placed  in  the  most 
favorable  position  along  the  curtains,  with  machine  guns  in  the 
most  important  redans. 

The  tenaille  and  the  tenaille  and  redan  trace  (Figs.  3  and  i.) 
are  objectionable,  in  that  they  involve  more  labor,  cannot  bring 
as  direct  a  fire  to  the  front,  and  the  faces  are  liable  to  enfilade 
when  the  salient  angles  approach  90°,  while,  on  the  other  hand, 
if  a  salient,  as  "S,"  Fig.  4,  approaches  120°,  mutual  defense  of 
the  faces,  "f  and"g,"  would  be  lacking,  thus  making  the  re- 
dan, "  R,'-  necessary.  This  trace  may,  however,  be  rendered  un- 
avoidable by  the  conformation  of  the  ground. 

The  cremaillere  trace  finds  special  application  in  a  position  such 
as  is  indicated  in  Fig.  5,  viz.,  joining  two  points,  one  at  the  top 
and  the  other  at  the  bottom  of  a  slope,  the  short  flanks  affording 
but  limited  opportunity  for  enfilade  fire. 

153. — Tlie  streiigtii  of  a  defensive  xiositioii  lies  in  a 
great  measure  in  the  proper  utilization  of  the  accidents  of 
the  ground;  thus,  the  traces  that  have  been  mentioned  may 
have  to  undergo  considerable  modification  to  be  appropriate  to 
the  varieties  of  terrain  constantly  met.  It  is  evident  that, 
in  a  broken  or  hilly  country,  one  by  preference  would  occupy 
the  heights.  These,  from  a  tactical  point  of  view,  possess 
the  advantage  of  overlooking  the  low  ground  in  front,  besides  the 
great  advantage  of  concealing  from  the  enemy  the  movements  of 
our  own  troops  in  rear ;  but,  since  all  else  must  be  subordinated 
to  fire  effect,  it  is  evident  that  such  a  line  on  the  heights  should 
be  selected  that  the  defenders  may  completely  cover  the  ground 
over  which  the  enemy  must  approach.  This  naturally  leads  to  the 
inquiry  as  to  how  that  line  may  be  determined. 

Heiglits,  great  or  small,  usually  present  the  profile  shown  in 
in  Fig.  7,  that  is  to  say,  they  have  a  steepest  slope,  "  b  c,"  which 
is  joined  to  the  crest  and  to  the  valley  below  by  the  two  gentler 
slopes,  "a  b"  and  "c  d.''  In  order,  then,  to  beat  the  zone  "b  c'' 
it  is  necessary  to  occupy  the  crest  "  c  "  or  some  point  below  it  on 
this  slope.  To  distinguish  this  crest  from  others,  it  will  be  called 
the  military  crest. 

With  the  inclination  of  this  steepest  slope  greater  than  one  on 
four,  it  is  unusual  to  construct  anything  but  shelter  trenches 
along  the  military  crest,  the  artillery  being  retired  sufficiently  and 


MHi  Field  Works  in  Combination. 

l)laceil  ill  Buch  positions  as  to  command  a  good  view  of  the  rest  of 
the  field.  With  gentler  slopes,  however,  the  artillery  may  be 
placed  at  intervals  along  the  military  crest,  the  intermediate 
spaces  being  held  by  infantry  in  shelter  trenches. 

A  better  disposition  than  this,  where  the  ground  permits  of  it, 
is  to  place  the  infantry  trenches  part  way  down  the  slope  in  front 
of  the  military  crest,  the  artillery  occupying  a  position  in  rear  of 
and  close  to  the  crest,  so  that  little  more  than  the  muzzles  of  the 
pieces  are  visible.  In  this  case  care  must  be  taken  that  the  in- 
fantry trenches  do  not  mask  the  fire  of  the  artillery. 

Ill  clioosiiijj;  a  defensive  ])ositi()ii  the  ground  should  be 
viewed  from  the  highest  point  in  the  vicinity  and  by  frequent 
practice  the  eye  so  trained  that  the  military  crest  is  at  once  ap- 
parent and  the  slopes  instinctively  classified  with  respect  to  their 
use  by  the  different  arms. 

Finally,  the  distance  to  a  number  of  visible  permanent  points 
in  front  of  the  works  should  be  determined  and  recorded,  so  that 
there  may  be  no  necessity  for  range  finding  during  the  enemy's 
advance. 


^NW." 


Slj.^ 


PLATE  22. 


Fig.l 


Fig.  2, 


Fig.  3. 


Fig.  4 


CllAPTKR  XII.     Siege  Works. 


154.  When  it  becomes  necessary  to  besiege  a  place,  it  may  be 
approached  by  common  trench  work  or  by  some  form  of  sapping. 
As  the  common  trench  and  the  flying  sap  are  the  work  of  infan- 
try, they  alone  will  be  referred  to. 

155. — The  method  of  providing  the  working  party  with  tools, 
laying  out  the  work,  and  extending  the  working  party  is  described 
in  Chap.  VIII.  It  is  to  be  noted,- however,  in  work  of  this  char- 
acter, til  (it  when  extending  along  a  zig-zag,  upon  reaching  the 
a)igle  the  order  of  forming  uj)  must  he  reversed.  Thus,  if  the 
column  from  b  to  c  (PI.  22,  Fig.  1)  were  forming  on  the  left,  upon 
reaching  e  f,  it  would  form  on  the  right. 

156. — Conimoii  Treiicli  Work.  This  may  be  used  as  a 
])jirallel,  an  oblique  approach,  or  communication.  The  work  done 
by  reliefs  in  constructing  a  parallel  is  shown  in  Fig.  2.  In  this 
case,  as  musketry  tire- must  be  provided  for,  the  second  relief  cuts 
out  the  top  step.  Should  it  be  necessary  to  revet  the  bottom  step, 
fascines  for  this  purpose  may  be  carried  by  the  second  and  third 
reliefs.  This  may  be  and  usually  is  omitted  until  the  parallel  is 
completed.  Fig.  3  shows  the  common  trench  used  as  an  oblique 
approach  or  communication.  Should  the  trench  be  found  wide 
enough  the  task  of  the  third  relief  may  be  omitted. 

157.— Tlie  Flying  Sap  (Fig.  4)  is  similar  to  common  trench 
work,  except  that  in  the  former  case  the  embankment  is  revetted 
with  gabions. 

In  taking  tools,  each  man  of  the  first  relief  is,  in  addition  to  his 
pick  and  shovel,  provided  with  two  gabions.  In  laying  out  the 
tools,  a  shovel  should  be  fastened  in  one  gabion  by  being  placed 
between  two  of  the  gabion  pickets,  handle  of  the  shovel  inside. 
A  pick  should  be  secured  in  the  other  gabion  by  having  its  point 
pushed  under  the  pairing  rods,  handle  inside.     The  gabion  with 


104 


SlKCK    Wc.KKS 


sliovcl  is  tjikcn  in  ihv  v\<^h\  liand.  the  one  with  ])ic'k  in  the  left: 
))(»tli  .u-;il)i()us  hciiii;'  caiM-ict]  l)y  cjin-yiii-   pickets. 

15S.  The  extension  in  the  Mvini:  sap  is  inadr  liom 
Bin,Li"]<'  rank  on  the  ri«j;iit  or  lolt,  and  ditlVrs  i'loiii  tin-  extrusion  in 
eoinmon  treneli  work  in  that  the  intervaL  in  the  former  case,  is 
tlie  widtli  of  two  ii-abions.  Each  man.  on  eomino^  into  line, 
places  his  ;^al)ions  so  that  llie\  toucli  each  other  alon,ii-  the  iimer 
cdL^'c  of  the  tai)e.  takes  out  his  tooLs  and  hiys  them  down,  as  ex- 
|)hnne(l  for  workinii'  ])arties  in  C'liap.  VIII.,  and  waits  for  tlie  com- 
mand. "('ommenc<'  work."  In  comnuMK-inu-  work,  tlie  ^'abions 
siiould  fii-st  l)e  tilled.  lienc(^  llie  position  of  each  pair  of  <4-ai)ions 
s^liould  l)e  I'cctitied  hefoi'c  this  command  is  .L;i\('n. 

151).  Ivicli  l)ranch  of  a  zi.u'za.L;-  should  recei\-e  sucli  (hri'ction 
as  not  to  expose  it  to  entilade  tii'c  from  any  ])oint  of  the  defenses. 
Its  })ro]()nLiation  sliould.  tluM-efore,  fall  oiitsi(h'  of  tlie  most  ad- 
vanced salient  of  the  c(.llateral  works.  ()rdinai-il\  it  would  not 
he  lon.u'cr  than  UK)  yds.  A  i)arallel  should  be  step])ed  in  ord(M-  to 
facilitate  an  a<l\ance  from  it. 

1()(>.  A  portion  of  the  ])arallels  and  a|)proaches  used  in  the 
eai)ture  of  t'ort  Wanner,  Morris  Island.  S.  C,  8epteml)er  Tth, 
IHCx],  is  shown  in  Tl.  '2'.). 


PLATE  23. 


9LATE  24. 


Figure  1. 


.3'  Figure  10. 

Figure  IL 


CHAPTER  XIII.     Defense  of  T^ocalities. 


161. — Walls.  Should  the  enemy  close  on  them,  walls  mvist 
be  so  prepared  that  they  will  neither  screen  nor  cover  him,  nor 
permit  his  firing  from  them.  To  prevent  this,  obstacles  may  be 
placed  in  front,  or  a  ditch  may  be  dug  outside  which  will  place 
him  so  far  below  the  top  of  the  wall  or  the  bottom  of  the  loop 
holes  that  he  cannot  fire  over  the  one  or  through  the  other.  A 
total  height  of  6  ft.  will  prevent  this,  or,  in  case  of  loop  holes  close 
to  the  ground,  the  maximum  height  should  not  be  greater  than  1 
ft.  from  the  outside,  or  an  embankment  made  in  rear  18  in.  high. 

Notwithstanding  these  precautions,  walls  may  still  give  cover, 
hence  they  should  be  flanked  when  possible. 

162.— Ill  jirepariiig  Avails  for  defense,  the  following 
cases  arise  :  — 

(1)  A  w^all  less  than  4  ft.  high.  Sink  a  small  trench  on  the  in- 
side to  gain  additional  cover.  Fire  over  the  top.  (PI.  24,  Pig.  1.) 
Head  cover  should  be  provided  with  logs,  sandbags,  or  sods,  sand- 
l)ags  being  the  best,  sods  next. 

Additional  protection  against  artillery  may  be  obtained  by 
heaping  earth  from  the  ditch  in  front  against  the  wall,  the  thick- 
ness depending  on  the  kind  of  artillery  the  wall  is  to  resist. 

If  this  should  be  done,  the  ditch  should  not  be  too  close  to  the 
wall.  A  trench  should  be  dug  in  rear  to  give  cover  to  the  sup- 
ports, or  for  the  firing  line  when  not  firing  from  the  wall. 

(2)  A  wall  between  4  and  5  ft.  can  be  used  as  it  stands,  subject 
to  the  same  modifications  as  in  the  preceding  case.     (Fig.  2.) 

(3)  Between  5  and  G  ft.  a  wall  can  be  notched.  The  tops  of  the 
notches  may  be  filled  with  sandbags,  sods,  etc.     (Fig.  3.) 

(4)  Should  the  w^all  be  higher  than  G  ft.,  a  i)latform  or  staging 
must  be  raised  inside  to  enable  the  men  to  tire  over  the  wall  or 
through  the  notches,  or  else  the  wall  must  be  loop-holed. 


110  Defense  of  Localities. 

1 03.- -L(00i)-IIoliiig.  Loop  holes  for  fire  should  not  be 
closer  than  2  ft.  6  in.;  ordinarily  they  should  be  3  ft.  To  find  the 
height  hold  the  rifle  in  the  position  intended  to  he  used. 

164.— To  make  a  loop  hole  in  a  wall  (Fig.  4),  14  in.  or  less  in 
thickness,  begin  on  the  inside,  to  prevent  the  splay  being  toward 
the  outside,  by  detaching  a  stretcher :  the  adjacent  header  on  the 
outside  can  then  be  knocked  out  and  the  loop  hole  roughly 
shaped.  Outside  dimensions,  4  in.  wide  by  3  in.  high.  Tnterior 
dimensions  will  depend  on  the  nature  of  the  grouml  over  which 
fire  is  to  be  delivered.  For  horizontal  fire  increase  the  breadth, 
for  elevated  or  depressed  fire  increase  the  height. 

In  walls  of  ordinary  thickness,  a  loop  hole  can  be  made  in 
about  15  minutes,  a  notch  in  about  5  minutes. 

165. — For  a  thick  wall  (Fig.  4),  the  small  part  should  be  at  the 
center,  the  loop  hole  splayed  to  the  front  and  rear,  for  it  will  do 
this  anyway.    The  side  toward  the  enemy  may  be  stepped,  in 
order  that  bullets  striking  it  may  flatten.    Loop  holes  of  obst^rva 
tion  should  splay  towards  the  outside. 

All  loop  holes,  when  not  in  use,  sliould  bo  blinded. 

166. — Tlie  lieiji^lit  or  position  of  tlio  loop  liole  is  in- 
fluenced as  follows : — 

(1)  1  ft.  above  the  ground.  Men  lying  down  in  a  shallow  exca- 
vation. Earth  heaped  up  to  18  in.  in  rear  prevents  the  enemy 
from  using  the  loop  holes  should  he  close  on  the  wall.  The  loop 
holes  are  a  difficult  mark  for  the  enemy  and  sentries  at  night  can- 
watch  the  sky  line.  Cannot  be  used  where  ground  in  front  is 
broken. 

(2)  Loop  holes  2  ft.  3  in.  Sitting.  Position  easy,  but  must  have 
a  deep  ditch  in  front. 

(3)  Loop  holes  3  ft.  Kneeling.  Position  strained  and  must 
have  a  deep  ditch  in  front. 

(4)  Loop  holes  4  ft.  4  in.  Standing.  Good  command,  but  easier 
mark  for  enemy :  ditch  necessary,  but  not  so  deep  as  in  cases  2 
or  3. 

(5)  Loop  holes  6  ft.  or  more.  Men  standing  on  banquette.  Best 
position  for  view  or  fire ;  no  ditch  in  front ;  banquette  strengthens 
wall,  but  takes  longer  to  prepare  wall  in  this  manner ;  more  sus- 
ceptible to  artillery  fire. 

167.^ — In  order  to  allow  a  double  tier  of  fire,  walls  should  be  at 
least  9  ft.  high.     (Figs.  5  and  6.) 


PLATE  25. 


Figure   1 . 


Figure  2 


Fioure  3 


Figure  6 


\ 


Figure  9. 


Figure  10 


Defense  of  Localities.  113 

108.  -Fences.  Fences  should  be  removed  or  left  standing 
according  to  their  jjosition  or  direction.  Wire  fence  forms  a  good 
obstacle,  a  rail  or  plank  fence  forms  a  screen  and  may  be  banked 
with  earth  to  giv^e  cover.  If  fence  is  of  stone  it  may  be  treated  as 
explained  for  walls. 

169. — Hedges.  Almost  the  same  principles  as  explained  for 
walls  apply  to  hedges.  A  hedge  primarily  acts  as  a  screen,  but  to 
resist  projectiles  must  be  banked  up  with  earth. 

Hedges  possess  the  following  advantages :  (1)  With  little  labor 
afford  good  cover.  (2)  Serve  as  a  screen  and  also  as  a  revetment. 
(3)  Act  as  an  obstacle  to  the  enemy. 

To  derive  these  advantages  hedges  can  be  treated  as  follows :  — 

(1)  A  hedge  with  a  ditch  on  the  defenders'  side.  Can  be  used 
as  it  stands,  the  ditch  being  converted  into  a  trench,  widened  and 
improved  if  necessary.     (Fig.  7.) 

(2)  A  hedge  with  a  ditch  on  the  enemy's  side.  Deepen  the 
ditch,  if  necessary,  and  throw  the  earth  to  the  defenders'  side 
to  give  cover.  If  this  is  not  possible,  scatter  the  earth  and  dig  a 
trench  in  rear.     (Figs.  8  and  9.) 

(3)  A  hedge  with  ditches  on  both  sides.  Deepen  the  ditch  on 
the  enemy's  side,  using  the  earth  to  obtain  cover.  Trench  on  de- 
fenders' side  may  be  deepened.     (Fig.  9.) 

(4)  Hedge  on  sloping  ground.  Gain  cover  by  a  small  trench  in 
rear ;  scarp  away  the  ground  in  front,  forming  a  glacis.     (Fig.  10.) 

(5)  High  and  strong  hedges.  When  time  is  available,  may  be 
treated  as  in  Fig.  11.  This  is  advantageous  where  additional  com- 
mand is  required. 

(G)  A  sunken  road  with  hedges  on  both  sides.  Dig  a  shelter 
trench  in  rear  of  the  hedge  on  defenders'  side  and  utilize  the 
earth  to  form  a  breastwork.  Cut  down  the  hedge  on  the  enemy's 
side,  entangling  it  to  form  an  obstacle. 

(7)  Hedge  without  ditches.  Excavate  a  shelter  trench  on  de- 
fenders' side  and  ])ank  up  the  earth  against  the  hedge  as  a  breast- 
work. 

Weak  j)laces  in  liedges  should  be  closed  up  with  boughs,  stakes, 
wire,  etc.,  as  a  strong  hedge,  in  addition  to  being  a  screen,  forms  a 
very  efficient  obstacle. 

ITO. — TCnibaiikmeiits  may  be  ddViuled:  — 

(1)  Narrow  Embankments.  By  occupying  the  inner  edge  bet- 
ter cover  is  obtained,  })ut,  unless  the  bank  is  both  low  and  narrow, 


114  Defense  of  Localities. 

there  is  a  dead  space  in  front  at  the  foot  of  the  outer  slope.  (PI. 
25,  Fig.  1.) 

(2)  Broad  Embankments.  By  occupying  the  front  edge,  a 
better  field  of  lire  is  obtained,  but  less  cover  can  be  jjrovided  for 
the  firing  line,  and  the  sui)])oits  aic  exposed  when  coming  into 
action.    (Fig.  2.) 

171." Cuttings  are  usu:ill\  tlctcndcd  on  the  defcndci-s' side, 
since  ill  this  case  retreat  is  easy  and  the  cutting  itself  forms  an 
obstacle  to  the  enemy's  advance.  But  for  active  defense  the  front 
edge  may  be  held  and  then  a  forward  movement  is  possible.  In  this 
case  a  means  of  retreat  must  be  jjrovided. 

172.  "Fig.  3  shows  a  case  where  the  fall  of  the  ground  admits 
of  botli  sides  of  the  cutting  being  occupied,  giving  a  double  tier  of 
tii(  .  1  he  command  of  the  higher  edge  over  th^  lower  should  be 
about  G  It. 

173. — In  case  of  a  road  cut,  as  in  Fig.  4,  the  vipper  fence  may 
be  used  to  sustain  a  breastwork,  while  the  hedge  below  may  be 
converted  into  an  obstacle. 

174.  A\ Oods.  (PL  26,  Fig.  G.)  Preparation  of  odoe  of 
Avood  occiii)ied.  The  edge  of  a  w^ood  should  be  put  in  a  state 
of  defense  and  an  abatis  is  the  readiest  means  of  doing  it.  The 
salients  should  first  be  prepared,  the  re-entrants  next  and  then 
roads  entering  the  wood  from  the  enemy's  side.  Instead  of  an 
abatis,  the  outer  trees  may  be  left  standing  and  an  entanglement 
made  by  packing  in  among  them  smaller  trees  cut  about  10  to  20 
paces  to  the  rear.  This  clearing  will  serve  as  a  communication  all 
round  the  edge  of  the  wood. 

If  a  re-entrant  bend  is  deep  the  abatis  or  entanglement  may  be 
carried  straight  across  it  and  flanked  from  the  adjacent  salients. 
In  case  of  a  road,  a  lunette  may  be  used  instead  of  the  abatis  or 
entanglement.  In  case  there  is  not  time  to  prepare  the  entire 
edge  of  the  wood,  the  salients  may  alone  be  prepared,  the  flanks 
of  the  defense  being  turned  back  for  a  short  distance  into  the 
wood. 

175.  Pre])aratioii  of  woods  lying  beyond.  Woods 
beyond,  witliin  rifle  range  of  the  line  of  defense,  but  too  far  to  the 
front  to  be  occupied,  and  too  extended  to  be  felled,  should  have  an 
abatis  or  entanglement  on  the  rear  side  to  act  as  an  obstacle. 

176.— Cover.  Trench  digging  is  difficult  on  account  of  the 
roots,  but  when  possible  it  should  be  done.     Cover  is  generally 


PLATE  20. 


Fig.  6 


%v-^ 


Defense  of  Localities.  117 

obtained  from  the  natural  features.  Trees,  unless  very  large  and 
standing  thickly,  do  not  give  complete  protection  against  artillery 
tire.  Troops  as  supports  and  reserves,  if  not  so  far  to  the  rear  as 
to  preclude  their  seeing  through  the  wood  to  the  front,  may  be 
co\erod  by  log  walls  and  trenches. 

ITT.  ('oiiiiiiiiiiicatioiis.  (a)  There  must  be  good  radial 
(M)iuiuunication  as  well  as  free  movement  along  the  boundary  in 
rear  of  the  firing  line. 

(1))  Roads  and  paths  for  bringing  u})  the  suiJi)orts  must  be 
clearly  marked  by  blazing  as  well  as  by  posting  sentries  at  all 
cross  roads. 

(c)  In  dense  woods,  preparations  should  be  made  for  blocking 
up  roads  by  cutting  trees  on  either  side  of  them  nearly  through, 
to  be  pulled  down  across  them  in  case  of  retreat. 

1T8. — Second  and  tliird  lines  may  be  placed  along  any 
open  space,  brook,  or  broad  road,  parallel  to  the  front.  In  case  of 
l)r()ok,  the  brook  should  be  in  fron^t  of  defenders'  jjosition. 

1  TO. — Artillery  should  generally  be  placed  outside  of  the 
wood  on  the  tltuiks.  'If  placed  in  the  wood,  batteries  should  be 
})laced  far  apart,  near  good  roads,  masked  as  much  as  possible  and 
each  gun  having  more  than  one  position.  Re-entrants  are  desir- 
able. 

The  number  of  defenders  is  estimated  at  2  to  3  men  per  yard  of 
front. 

180.— Stockades.'  Stockades  are  timber  defenses,  made  by 
Ijlacing  one  or  niore  rows  of  timbers  or  rails,  upright  or  horizon- 
tally, and  so  close  to  one  another  as  to  keep  out  rifle  bullets, 
loop  holes  being  made  through  which  fire  is  delivered.  They 
have  the  advantages  of  combining  a  parapet  and  an  obstacle  in 
one,  giving  good  cover  and  ample  interior  space,  and  of  being 
easily  guarded  against  surprise.  On  the  other  hand,  they  re- 
quire considerable  time  for  construction,  a  certain  amount  of  skilled 
labor,  and  are  easily  destroyed  by  artillery  fire. 

181. — Stockades  Avould  be  enii)loyed:  — 

(1)  Where  timber  is  plentiful. 

(2)  When  artillery  tire  is  not  to  be  resisted. 

(3)  When  acting  purely  on  the  defensive.  They  are  useful  for 
the  rear  faces  or  gorges  of  enclosed  works,  and  may  be  a  good  deal 
used  in  the  defense  of  houses,  streets,  villages,  and  even  woods. 

182.— Stockades  of  vertical  timbers.    Vertical  timbers 


118  I  )i;i'i:nsk  ok   I^ocalii'i  ks. 

sliould  Ix'  close  lo!4Tt  li(M\  ])lan1<'(l  in  \]\v  ground  to  a  (l(>])tli  of  .*>  or 
\  ft..  accoi-diiiLi-  to  their  size  and  \veii:ht.  pointed  oi-  spiked  at  the 
toj).  and  loo|)  holed  at  intei'vals.  A  rihand  must  he  s])ik(Ml  aloni*' 
the  iusitlc.  near  the  top.  to  keep  the  tinihers  close  toiictlHM". 

I  S;5.  PI.  "J.').  l^')<^s. ."),(').  and  7.  show  stoclvades  w  ith  squared  tim- 
IxM's:  l''i,Li'.  S  wit  li  round  tinihei-s  S(iuared  wliere  they  touch  and 
tlie  joint  hetween  every  two  trees  made  uood  on  the  inside  by 
a  smaller  tree. 

I  SI.  The  loop  holes  should  he  made  in  the  crack  hetween  the 
timbers,  in  order  to  asoid  weakening"  them,  half  hein^'  cut  out  of 
each.  (FiK-  ^•)  In  round  tind)er.  two  saw  cuts  will  make  a  looj) 
hole.     (Fi^.  10.) 

185. — The  loop  holes  should  be  cut  before  the  timbers  are 
])lac(Hl  in  jjosition  and  the  same  precautions  in  regard  to  them  as 
given  in  walls  should  be  observed.  A  loop  hole  can  be  cut  in 
from  10  to  15  minutes.  • 

1  S(). — Tn  the  foregoing  cases,  where  the  stockade  is  built  of 
timl)ers  |)lace(l  vert ically,  squared  tindx^rs  are  preferred,  as  they 
are  more  easily  fastened  togethei-  and  the  joints  made  bullet 
proof.  In  round  timl)ers  the  logs  sliould  be  as  straight  as  possi- 
bl(\     If  very  erooked,  two  eom])lete    rows  will  l)e  rcMjuired. 

()n(^  X.  C  ().  and  K*  men  will  ertn-t  b")  running  fcM't  of  stockade 
of  squai-od  tind)er.  with  one  tier  of  loo])  holes,  in  8  hours. 

1  ST.  Stockados  of  liori/.oiital  tinihers,  iron  rails,  fas- 
cines, or  logs.     (PI.  26.) 

Fig.  1  shows  stockade  of  rails  and  ties.  Can  only  be  used  for  a 
very  short  distance  as  it  will  involve  an  immense  amount  of  plant. 
Can  be  used  to  cover  guns,  close  a  road,  and  is  more  properly 
a  barricade. 

Fig.  2  shows  a  stockade  or  log  breastwork,  banked  in  rear  with 
earth  held  in  place  by  planks  or  hurdles  and  stakes. 

Fig.  3  shows  a  stockade  or  breastwork  of  logs  and  fascines. 

1 88.  Stockade  work,  both  vertical  and  horizontal,  can  be 
used  for  the  construction  of  ((onbours  (Figs.  4  and  5)  and  capon- 
h'i's  for  flanking  walls  or  stockades  and  covering  entrances.  Tam- 
bours may  be  triangular  or  rectangular  in  shape,  arranged  for  one 
or  two  tiers  of  lire,  and  covered  with  a  splinter-proof  roof. 

1  81).>  Biiildiiio's.  Buildings  may  be  used  for  defense, either 
singly  or  in  cond)ination: 

(a)  As  tactical  jjoints  in  the  l)attletield,  held  either  as  advanced 


Defense  of  Localities.  119 

posts  or  as  supporting  points  in  the  line,  or  on  the  flanks,  or  as 
rallying  points  to  cover  retreat. 

(b)  As  keeps  to  a  more  extensive  position,  such  as  a  wood,  vil- 
lage, etc. 

(c)  As  an  isolated  post  on  the  lines  of  communication. 

190. — In  order  to  admit  of  use  as  a  defensible  post,  a  building 
should  possess  the  following  requisites: — 

(1)  Solidly  built  of  soft  stone,  brick,  or  adobe. 

(2)  Large  enough  to  hold  at  least  half  a  company. 

(3)  Sheltered  from  distant  artillery  fire,  otherwise  the  building 
cannot  be  held  against  infantry  or  cavalry. 

(4)  Well  selected  for  the  object  in  view. 

(5)  Low,  flat  roof. 

(6)  Clear  field  of  fire  obtainable. 

(7)  Shape  in  plan  affording  flank  defense. 

191. — The  building  should  be  looked  upon  as  a  keep,  or  second 
line  of  defense,  a  first  line  being  prepared  at  a  minimum  dis- 
tance of  40  yds.  to  the  front,  this  distance  being  the  least  that 
will  give  the  defenders  immunity  from  splinters  caused  by  shells 
striking  the  building. 

192. — 111  falling  back,  the  first  line  should  retreat pasf,  not 
into  the  house,  which  should  by  this  time  be  occupied  by  the  sup- 
ports. The  garrison  of  the  house  may  be  estimated  at  two  men  to 
each  door,  window,  or  loop  hole,  with  a  reserve  of  one-fourth,  tac- 
tical unity  being  in  this,  as  in  all  similar  cases,  adhered  to  as 
much  as  possible. 

193. — The  following  are  the  steps  which  must  be  taken  in 
hastily  preparing  a  house  for  defense: — 

(a)  Remove  the  inhabitants,  also  all  easily  combustible  mate- 
rial, and  provide  water  and  heaps  of  earth  in  each  room. 

(b)  Barricade  doors  and  ground-floor  windows  (bullet  proof  if 
possible),  also  mask  inaccessible  windows,  and  remove  all  glass. 

(c)  Make  loop  holes  in  doors,  shutters  and  walls,  and,  in  the 
case  of  a  sloping  roof,  remove  tiles  or  slates. 

(d)  Clear  away  cover  in  the  vicinity  as  far  as  time  and  means 
will  allow. 

(e)  Open  up  communication  throughout  and  prepare  a  means  of 
retreat. 

194. — The  same  precautions  as  to  loop-holing  walls  apply  in 
case  of  buildings.     On  the  ground  floor  the  horizontal  dimension 


1-0  Defense  of  Localities. 

of  a  loop  hole  should  be  greatest ;  on  upper  floors,  the  vertical 
dimension.  If  an  artillery  attack  is  feared,  shelter  trenches 
should  be  provided  outside  the  building  on  the  flanks. 

195.  -l$arrieades  for  Doors  may  be  made  in  the  following 
wjiys: 

(a)  Fill  boxes,  barrels,  cupboards,  etc.,  with  earth  and  i)lace 
them  against  the  door  inside. 

(b)  Build  a  wall  of  brick,  stone,  flag-stones,  or  hearth-stones, 
against  the  door  inside,  and  support  by  a  shutter  or  another  door. 

(c)  If  railway  plant  is  available,  pile  ties  horizontally  on  one 
another  and  secure  with  telegraph  wire. 

(d)  Pile  lumber  inside  the  door  and  flx  with  blocks  nailed  to 
the  floor. 

(e)  Other  methods  may  be  employed  in  accordance  with  mate- 
rial available. 

196. — Should  a  door  be  reserved  for  use,  it  should  be  in  a  re- 
ciitcrinir  an^^lr  of  the  building,  if  possible,  and  protected  from 
tire.  A  couple  of  chests  fllled  with  earth  and  jjlaced  on  rollers 
may  be  used  to  secure  the  door.  Similarly  it  may  be  possible  to 
place  iron  or  wood  on  the  door,  thus  rendering  it  bullet  proof. 

197  >\'in(loAvs.  Windows  must  be  barricaded  as  explained 
for  doors.  If  provided  with  shutters,  these  should  be  utilized. 
Upper  windows  require  to  be  bullet  proof  only  high  enough  to 
cover  the  defenders.  Bedding  is  no  protection  against  modern 
rifles,  but  may  be  used  to  mask  windows  of  upper  floors.  If  tim- 
ber is  used  it  should  be  placed  vertically  and  nailed  to  horizontal 
ribands  strutted  back  to  the  floor. 

198. — If  the  house  is  large  and  strong  and  is  to  be  held  to  the 
last,  in  addition  to  the  foregoing,  the  following  preparations 
should  be  made: 

(1)  Arrange  for  storage  of  provisions  and  ammunition. 

(2)  Set  apart  a  place  for  a  hospital. 

(3)  Prepare  latrines. 

(4)  Loophole  partition  walls  and  upper  floors. 

(5)  Make  ready  barricades  to  cover  retreat  from  one  part  of  the 
building  to  another. 

(6)  If  artillery  is  feared,  shore  up  the  floors  and  cover  them 
with  about  3  in.  of  earth. 

199. — Should  the  construction  of  the  house  not  afford  suffi- 
cient flank  defense,  it  can  be  improvised  in  the  shape  of  tambours 


^ifX 


PLATE  27 


Fig  2. 


Fig.  6, 


yrrrftflttrfHtttrtttltflrtV 


fmfiTtfmff.,,,  , 

.  ww\\k  \%. ^,:  K, s, < 

V  \  V  "^  V  ^  \  X  A  <».  ^'  ,^  ^ 


Defense  of  Localities.  123 

or  caponiers,  but  the  labor  involved  in  their  construction  is  con- 
siderable and  they  would  only  be  undertaken  for  the  defense  of 
a  very  long  wall  or  to  cover  an  important  entrance  or  communi- 
cation. 

For  the  latter  purpose  a  macliicouli^  gallery  is  sometimes  em- 
ployed. (PL  27,  Fig.  3.)  This  is  made  by  removing  the  wall  of 
the  upper  story  where  a  window  occurs  down  to  the  level  of  the 
floor,  running  out  two  or  three  long  balks  so  as  to  project  a  few 
feet  beyond  the  wall,  the  other  ends  being  secured  down  to  the 
floor.  On  these  planks  are  nailed,  with  holes  cut  through  to  act 
as  loop  holes,  and  a  musket-proof  parapet  of  planking,  sand-bags 
etc.,  is  built  all  around.  A  projecting  veranda  offers  a  favorable 
position  for  this  arrangement. 

Second  method :  If  a  regular  gallery  can  not  be  made,  holes 
may  be  cut  in  the  wall  at  a  convenient  height  for  a  man  to  fire 
downwards  when  leaning  over,  and  a  screen  of  wood  or  other  ma- 
terial may  be  secured  outside  for, protection.     (Fig.  4.) 

If  neither  of  the  foregoing  methods  be  i)OSsible,  holes  may  he 
made  in  the  roof,  through  which  grenades  may  be  thrown  on  the 
enemy. 

200.— The  materials  most  likely  to  be  useful  in  preparing  a 
house  for  defense  are  sand-bags,  stout  timbers,  such  as  railway 
ties,  large  boxes,  chests,  barrels,  coal-boxes,  furniture  and  bed- 
ding. 

201.— PI.  27,  Figs.  1,  2  and  5,  illustrate  the  more  important 
points  in  the  defense  of  a  house. 

202. — Farms.  Farms  should  be  defended  according  to  the 
nature  of  the  surface  covering,  the  ground  and  the  improvements, 
and  may  involve  the  preparation  for  defense  of  walls,  hedges,  cut- 
tings, embankments,  buildings,  woods,  etc.  Owing  to  their  posi- 
tions, farms  may  become  very  important  and  a  great  amount  of 
fighting  take  place  for  their  possession.  They  may  occur  either 
in  the  main  line  of  a  position,  as  an  advanced  post  in  front,  or  as  a 
reserve  station  or  rallying  point  in  rear. 

203. — Fig.  G  shows  the  principles  of  defense  apijlied  to  a  farm 
lying  in  advance  of  a  stream,  which  is  a  point  that  requires  In  he 
strongly  held.  From  the  position  of  the  farm  it  must  be  held  as 
an  advanced  i^ost. 

The  firing  line  is  established  along  the  fences  bounding  the 
fields  and  orchard.     The  farm  buildings  are  loop-holed  and  can 


1-i  Dffknst:  of  Localities. 

Ijc  held  should  the  liring  line  be  forced,  while  the  fire  from  the 
house  would  render  occui^ation  of  the  farmyard  l)y  the  enemy 
diffieult.  Further  to  the  rear,  the  wood  is  strongly  prepared  foi-  a 
tinal  jinsitioii.  as  shown  in  the  figure. 

LM)I.  ^rhc  real- (.r  an  advanced  post  slionld  he  left  weak  and 
ojicn  to  facilitate  i-ci-aj)tiirc. 

2<)5.  \'  illa«>;es.  Villages  can  l)e  ra])idly  ])i-e})arcd  for  defense 
and.  nndcr  favorable  circumstances,  obstinately  defended:  conse- 
(|uently  they  ai'e  va]iial)Ie  sujjporting  i)oints  in  a  defensive  line. 
Owinu"  to  the  ellVct  of  modern  artillery  and  tlie  ai)ility  of  l)nrst- 
in^-  shells  to  set  \  illages  on  fire,  great  i)i-ecautions  Ikinc  to  he 
taken  in  the  i)re|)arati()n  for  defense. 

LM)(>.  A  Nillau'c.  when  ])ro]ierly  pi-ej)ared  and  d(>fended,  may 
have  the  following  advantages: 

(a)  Can  l)e  rapitlly  placed  in  condition  for  delense. 

()))  Defense  may  be  ohstinate     thus  giving  time. 

(c)  Conceals  the  sti-ength  of  the  deh-nders. 

(d)  Provides  a  certain  amount  of  covei-  from  tire. 
•    (e)  Shelter  from  the  eh'ments. 

On  the  other  hand: 

(a)  The  gaiivison  is  scattered,  hence  the  difTundty  of  sujier- 
\  ision. 

(I))  When  under  artill(>ry  tire.  s])linters  may  cause  many  casu- 
alties. 

(c)  Liability  to  be  set  on  hre  l)y  shells. 

207.  — A  village  may  be  held  with  the  following  objects  in 
view: — 

(a)  As  a  supporting  point  in  the  main  line  of  defense. 

(b)  As  an  advanced  post  in  front  of  the  main  line. 

(c)  As  an  independent  post. 

(d)  As  a  reserve  station  or  rallying  point  in  rear. 

In  the  first  case,  strengthen  the  front  and  flanks.  The  rear 
should  be  prepared  to  resist  infantry.  In  the  second  case,  the 
distance  from  the  main  line  will  govern  the  amount  of  prepara- 
tion. If  very  distant,  should  be  j^repared  for  all-round  defense. 
If  within  rifle  range,  the  rear  should  he  left  open,  so  that  in  case 
the  village  is  taken,  recapture  will  be  facilitated.  In  the  tJiird 
case,  if  an  independent  post,  must  be  prepared  for  an  all-roimd 
defense.  In  the  fotirth  case,  if  in  the  rear  of  the  main  line,  must 
l)e  i)repared  for  a  protracted,  all-round  defense. 


PLATE  28. 


C3  House  t(ft  standing 

□        -     fV^Pf^f^  for 

demoiiuoJi. 
^S        •     preparpii  for  defense 
mmmm^  K lit refxch mftit 
ZZZ2,\  Wire  entanglement  ^f^^2$^' 


L 


Defense  of  Localities.  127 

208.-  Whether  or  not  a  village  is  to  be  held  will  depend  on: — 

(1)  Its  tactical  value  as  compared  with  the  number  of  men  re- 
quired to  defend  it. 

(2)  Whether  it  is  practicable  to  provide  a  sufficient  garrison 
for  its  defense. 

(3)  Whether  it  will  be  possible  to  demolish  the  village  entirely, 
in  order  to  deprive  the  enemy  of  the  cover  it  provides. 

(4)  On  the  form  and  nature  of  the  surrounding  country,  i.  e., 
no  commanding  ground  within  artillery  range,  foreground  easily 
preimred  and  the  unimx^eded  advance  of  the  defenders'  troops  in 
the  required  direction  easily  arranged. 

(5)  On  the  shape  of  the  village — whether  broadside,  salient,  or 
circular. 

(6)  Nature  and  materials  of  the  houses. 

209.^ — The  first  points  to  determine  in  preparing  a  village  for 
defense  are  how  much  of  it  will  be  defended,  whether  there  are 
buildings  suitable  for  a  keep  or  citadel,  and  whether  or  not  these 
are  jn-operly  located. 

210. — The  arrangements  for  defense  would  be  made  in  the 
following  order: — 

(1)  Clear  the  ground  toward  the  enemy.     (See  Chap.  V.) 

(2)  Cover  for  the  firing  line,  supports,  and  reserves.  (See 
Chap.  IV.) 

(3)  Creating  obstacles.     (See  Chap.  VI.) 

(4)  Preparing  communications.     (See  Chap.  XVII.) 

(5)  Constructing  retrenchments,  citadels,  or  keeps.  (See  "Build- 
ings."') 

211. — The  garrison  of  a  village  may  be  estimated  at  tw^o  men 
to  the  yard  of  perimeter  to  be  defended. 

212.— Salient  Villag-e.  (PI.  28,  Fig.  2.)  The  successive 
lines  of  defense  must  be  carried  well  out  to  both  sides  and  the 
flanks  well  protected,  otherwise  the  enemy  may  turn  them  and 
avoid  fighting  in  the  streets. 

213.  —  Broadside  Village.  (Fig.  1.)  Here  the  outside 
fences  must  be  more  utilized  than  the  actual  buildingS;  as  the 
latter  are  open  to  fire  from  artillery. 


1-S  Defknst-:  of  Locatjtif.s. 

214. -Circular  \'illii<j,v.  (PI.  2'J.)  Cheat  attention  must 
be  paid  to  the  proper  division  of  the  village  into  sections  for  de- 
fense and  preparing  and  making  the  communications. 

21  5.  In  any  of  the  foregoing  cases,  if  cover  does  not  exist  for 
8ui)i)orts  and  reserves,  it  must  be  provided,  as  the  village  will 
I)robably  be  shelled  before  being  assaulted. 

If  artillery  is  to  be  used  it  should  be  placed  on  commanding 
ground,  inaccessible,  if  possible,  to  the  enemy,  and  so  that  its 
tire  will  sweej)  those  paits  most  la\(»i;il)le  to  the  enemy's  ad- 
vance. 


PLATE   29. 


8ITY 
iLFbRNlA- 


-^ft^SE  ape,. 


CIIAPTEK  XIV.     Use  of  Cordage  and  Spars. 


210. — A  rope  is  composed  of  three  or  more  strands  of  fibrous 
material,  iron  or  steel,  twisted  together.  The  strands  of  fibrous 
ropes  are  formed  of  threads;  of  iron  and  steel  rojjes,  of  wires. 
The  size  of  rope  is  denoted  by  its  diameter  in  inches,*  and  is  gen- 
erally sold  by  the  pound.  Fibrous  ropes  when  new  and  dry 
stretch  considerably,  when  wet  they  contract ;  advantage  is  often 
taken  of  the  latter  fact  to  tighten  temporary  lashings.  Manila 
rope  is  only  about  %  as  strong  as  hemp  rope ;  tarred  ropes  only 
about  %  as  strong  as  untarred. 

217. — A  rule  approximating  to  the  breaking  tveiglit  of  a  new 
rope,  in  tons  of  2,000  lbs.,  is  to  take  one-fourth  the  square  of  the 
circumference  in  inches.  The  strength  of  pieces  from  the  same 
coil  may  vary  25  per  ct. 

Ropes  in  daily  use  should  not  be  worked  up  to  greater  than 
I  their  breaking  loads,  to  'meet  the  reduction  in  strength  by 
wear  and  exposure. 

21 8.— The  .following  table  gives  the  approximate  breaking 
loads  and  weights  of  new  Manila  ropes,  Swede's  hemp  center 
Iron  pliable  ropes  of  6  strands  of  19  wires  each,  and  hemp  center 
Steel  pliable  ropes  of  6  strands  of  19  wires  each,  Manufacturers' 
Tests  : 


*  In  the  Navy  the  size  of  rope  is  denoted  by  its  circumference  in  inches.     The  method 
used  should  be  distinctly  stated. 


i;j2 


Use  of  Cokdj 


.\(ii;     AM)     Sl'Alv'S. 


Diam.  in 
inches 

Breaking  loads  In  lbs. 

Weight  per  100  ft. 
in  lbs. 

Minimum  Size  or 

Sheaves  in  feet 

for  Iron  and  Steel 

Manila 

Iron 

steel 

Manila 

Iron  & 
Steel 

1-4 

780 

3 

3-8 

1,280 

5,000 

5 

26 

1 

7-16 

1,562 

6,200 

12,000 

QH 

29 

IJ2 

1-2 

2,250 

7,600 

15,000 

8 

35 

2 

'    5-8 

4,000 

11,000 

24,000 

13.5 

70 

2U 

3-4 

i>,000 

17,500 

36,000 

16.5 

88 

3M 

7-8 

7,500 

23,000 

50,000 

24 

120 

3K 

1 

9,000 

32,000 

66,000 

30 

158 

4 

IM 

14,000 

54,000 

104,000 

45 

250 

5 

1^3 

20,250 

78,000 

154,000 

66 

365 

QH 

I'U 

30,250 

108,000 

212,000 

97 

525 

^H 

o 

36,000 

130,000 

250,000 

115 

630 

9 

219. — Knots,  Hitelies,  etc.  The  standing  part  of  a  rojje 
is  any  ])art  not  an  end. 

.1  hi(jht  is  a  loop  formed  in  a  rope.     (PI.  30,  Fig.  1.) 

Whipping  is  securing  the  end  of  a  rope  with  twine  to  i)r('\(Mit 
it  from  fraying  out.     (Fig.  1.) 

Parceling  is  wrapping  a  rope  to  prevent  chafin<^-  or  cutting- 
against  a  rough  surface  or  sharp  edge.     (Fig.  1.) 

Stop)ping  or  seizing  is  fastening  two  parts  of  a  rope-  t<)<;('thor 
without  a  crossing  or  riding.     (Figs.  1  and  17.) 

Nipper ing  is  taking  turns  crosswise  between  the  i^arts  to  jam 
them.     (Fig.  1.) 

Splicing  is  joining  the  ends  of  ropes  by  opening  the  strands 
and  placing  them  inot  one  another  (Figs.  2  and  3),  or  by  i^utting 
the  strands  of  the  ends  of  a  rope  between  those  of  the  standing 
part.     (Fig.  4.) 

Boiling  or  stopper  hitch  for  fastening  a  rope  to  a  strap  or  tail 
block,  and  to  secure  a  fall  while  being  shifted  on  a  windlass  or 
capstan.     (Fig.  5.) 

Overhand  knot  to  prevent  the  end  of  a  rope  from  fraying  out, 
from  slipping  through  a  block,  and  the  beginning  of  several  other 
knots.    (Fig.  6.) 

Figure  of  8  knot,  used  in  making  cask  i^iers.     (Fig.  7.) 


PLATE  30. 


TG.2. 


FIG.l 


or  Sezzirro  ' '  *=* 


FIG.  6 


'ye  Sfdtce  PIG7 


^«r^M«/2^^   knot  ^^""''^    ¥   ^ 

pIG.ll.,^ FIG.12. 


Sinole  bow  ^slipknot      j.^    TT^  ^     Square  or ,   .    Thie/^      GrnrnM 

FIG  13.  ^-^^  tfk  ^^FIG14.  .^ 

(c       m 


hitchy. 


FIG.  17,     p^^l*'*/'^'^*^ : 


Double 
'avers  knot 
Sheet  bervd.        Bend 

FIG.22. 


Timber  hitch. 


^A-ff- 


PLATE  51. 


FIG.l 


FIG.  2.  FIG.  3^       FIG.4.^     FIG.5. 


Blackwall  ^CamckSmd 

IG.9. 


Rack  las/ung^^^'''-^ f^y 
FIG  15  ■^      V\!,\5-^^'^^  SiguZeZashing 

^^         V  ^\K,  /  FIG.  16, 


Shear  IjashinQ 


Gin    la^Un^ £A.lf. 


PI.  31,  Fig.  7^revewe  rcvpe  ia  tlie  three  left  ami  the  two  extreme  right 
(M'ossiiigs. 


Use  of  Cokdack  and  Si'Aiis.  137 

Square  of  reef  knot  for  joining  the  ends  of  two  ropes  the  same 
size.     (Fio-.  8.) 

Til  ief  Ji  not  (Fig.  d),  with  ends  on  opposite  sides,  and  Grannij 
kitot  (Fig.  10),  by  crossing  the  ends  the  wrong  way,  both  looking 
like  square  knots,  are  to  be  avoided,  as  they  will  not  hold. 

Siiitjle  Jh)U'  or  sU^)  knot.     (Fig.  11.) 

S<pi(ire  hoir,  which  can  be  cast  off.     (Fig.  13.) 

Marlinnpike  hitch,  used  in  putting  on  lashings,  etc.     (Fig.  12.) 

Sheepshank,  used  to  shorten  a  rope  temporarily  without  cut- 
ting.   (Fig.  14.) 

Tico  half  hitches,  for  fastening  the  end  of  a  rope  around  its 
own  standing  part.     (Fig.  15.) 

Round  ttirn  and  ttvo  half  hitches,  to  secure  guys  to  stakes,  etc. 
(Fig.  16.) 

Fisherman/ s  hend  or  Anchor  knot,  for  fastening  a  rope  to  an 
anchor  or  ring.     (Fig.  17.) 

Weavers  knot  or  sheet  hend,  for  joining  ropes  of  different  sizes 
without  jamming.     (Fig.  18.) 

Doid)le  sheet  hend,  more  secure  than  the  single  bend.   (Fig.  19.) 

Clove  hitch,  for  fastening  a  rope  to  a  sj^ar;  the  end  may  after- 
wards be  stoppered  to  its  own  part.  The  clove  hitch  differs  from 
two  half  hitches  only  in  being  made  around  a  spar  or  other  rope 
instead  of  around  its  own  standing  part.     (Fig.  20.) 

Timher  hitch  jams  when  made  round  a  timber.     (Fig.  21.) 

Bowline,  to  form  a  temporary  loop  at  the  end  of  a  rope.  (Fig. 
22.) 

BowJine  on  a  hight,  to  make  a  loop  on  a  bight.     (PI.  31.  Fig.  1.) 

Cat's  pau',  for  applying  a  purchase  or  tackle  to  the  fall  of  an- 
other.    (Fig  2,  the  beginning;  Fig.  3,  how  applied.) 

Blackicall  hitch,  for  fastening  the  end  of  a  rope  on  a  block  in 
the  simplest  manner,  or  fastening  a  rope  in  a  hook.     (Fig.  4.) 

Mousing  is  a  seizing  placed  around  a  hook  to  prevent  it  from 
spreading  or  unhooking.     (Fig.  4.) 

Carrick  hend,  to  fasten  guys  to  a  derrick.     (Fig.  5.) 

Lark's  head,  for  fastening  a  bight  to  a  ring.     (Fig.  0.) 

Capstan  or  Prolonge,  making  fast  a  spar.     (Fig.  7.) 

Wall  knot,  for  finishing  off  the  end  of  a  rope  to  keep  from  un- 
stranding  (Fig.  8),  by  passing  the  strands,  as  shown,  then  draw- 
ing them  down  into  a  knot. 


\->^  I'sK  oi-    ( '()!:i)  \(.i-.   AM)  Si'  \i:s. 

Fn([>pin(j  is  i>iissiiig  a  rope  around  a  Jasliiii^-  to  kc^i)  \hv  turns 
to<,^ether.     (Figs.  14,  15  and  16.) 

Straps  ?iVG  rings  used  for  attaching  tackles  to  spa  is  or  ropes. 
(PI.  3;3;  Figs.  1,  2  and  6.) 

220.  To  make  a  slioit  splice.  (PI.  30,  Fig.  2.)  Unlay 
strands  of  each  end  for  a  convenient  length ;  take  an  end  in  each 
hand,  place  end  to  end,  strands  sandwiching,  and  grasp  the  three 
strands  from  opposite  rope  in  left  hand.  Take  a  free  strand,  pass 
it  over  the  first  strand  next  to  it,  then  through  under  the  second 
and  out  between  the  second  and  third  from  it,  then  haul  taut. 
Pass  each  of  the  remaining  six  strands  in  same  manner,  first 
those  of  one  end  and  then  those  of  the  other,  and  so  continue  as 
far  as  desired. 

221.  To  make  a  loii*:^  splice.  (Fig.  3.)  Unlay  strands 
of  each  end,  3  or  4  times  longer  than  for  short  splice,  and  place 
end  to  end  as  described.  Unlay  one  strand  a  considerable  dis- 
tance and  fill  up  its  space  with  opposite  strand  from  other  rope, 
and  twist  them  together.  Do  the  same  with  two  strands  on  other 
rope.  Open  remaining  strands,  divide  in  two,  make  overhand 
knot  with  opposite  halves,  and  lead  ends  as  in  short  splice.  Cut 
off  the  other  two  halves.  Do  the  same  with  the  other  pairs  of 
strands  where  twisted  together.  Before  cutting  off  any  of  the 
half  strands,  first  stretch,  roll  under  the  feet,  and  pound  the  rope 
well.  This  splicing  does  not  increase  the  size  of  the  rope  and  is 
used  where  the  spliee  is  to  run  through  blocks. 

222.  To  make  an  eve-splice.  (Fig.  4.)  Unlay  one  end 
for  short  distance,  lay  strands  upon  the  standing  part  so  as  to 
form  the  desired  sized  eye.  Put  first  end  through  the  strand  next 
to  it.  Put  second  over  that  strand  and  through  second.  Put 
third  through  third  strand  on  other  side  of  rope  and  so  continue. 
This  forms  a  permanent  loop  in  end  of  rope. 

223. — To  sliii|2:  a  box  or  barrel.  Lay  a  long  strap  under 
it.  spreading  the  parts,  and  pass  one  bight  through  the  other  ;  or, 
make  a  long  loop  witli  a  l)owline'  and  sling  as  show^n  on  PL  31, 
Fig.  11  If  one  head  is  out  stand  barrel  up.  put  one  part  of  a  strap 
under  middle  of  1)  )ttoni,  take  ii  half  hitch  over  top  with  each  part 
just  over  bilge  hoops  and  exactly  opposite ;  or  place  rope  under 
V)arrel,  bring  up  over  top.  make  overhand  knot,  open  it  out  and 
slip  each  half  down  over  hoops,  fasten  end  to  standinii'  part  with 
bowline.     (Fig.  10.) 


PLAIE'32. 


FIG.l.  _FIG.2        FIG.  3.-        FIG.4. 


FIG  5. 


■Wig.  6. 


FIG  7 


FIG  10 


HrryBlock 


UsE~OF  Cordage  and  S['aks.  141 

224.— liack  lasliiiigs  (Figs.  11,  12  and  13)  are  made  with  a 
}{ in.  rope,  18  ft.  long  with  a  loop  at  one  end,  and  a  rack  stick 
2  ft.  long,  IJ^  in.  in  diameter  having  a  cord  4  ft.  long  through  one 
end,  by  passing  the  rope  two  or  three  times  around  the  side  rail 
and  balk,  and,  after  making  it  fast,  twisting  it  tightly  with  the 
rack  stick. 

225.— Transom  lasliiii<>:.  (Fig.  11.)  The  spars  are  laid 
across  each  other  at  right  angles,  a  clove  hitch  is  made  on  one  of 
the  spars,  the  end  then  twisted  around  its  standing  part,  then 
three  or  more  turns  are  taken  around  the  spars,  under  one  and 
over  the  other,  keeping  outside  previous  turns  on  one  spar  and 
inside  on  the  other.  Several  frapping  turns  are  then  taken  be- 
tween the  spars  and  the  end  fastened  on  one  of  the  spars  with  a 
clove  hitch.  Used  in  lashing  transoms  to  standards  in  bridge 
building. 

226.— Shear  lasliiiig.  (Fig.  15.)  The  spars  are  laid  par- 
allel, a  couple  of  inches  apart,  on  a  block,  a  clove  hitch  made  on 
one  spar,  then  5  or  6  turns  taken  around  both  spars  without  rid- 
ing. Several  frapping  turns  are  then  taken  between  the  spars 
and  the  end  fastened  on  one  of  the  spars  with  a  clove  hitch.  This 
is  used  in  rigging  shears  for  hoisting  heavy  weights,  etc. 

227.— Gill  lasliiiig.  (Fig.  16.)  The  three  spars  are  laid 
parallel,  a  couple  of  inches  apart,  the  butts  of  the  two  outside 
ones  in  one  direction,  that  of  the  middle  one  in  the  opposite  direc- 
tion. A  clove  hitch  is  m-ade  oi^  one  spar,  then  5  or  6  loose  turns 
taken,  passing  over  and  under,  without  riding.  Several  frapping 
turns  are  taken  in  each  interval  and  the  end  fastened  on  one  of 
the  spars  with  a  clove  hitch. 

228.— 351c)eks,  Tackles,  etc.  Ajndley  consists  of  a  wheel, 
having  a  grooved  rim  for  carrying  a  rope,  turning  in  a  frame.  (PL 
32,  Fig.  1.) 

A  block  (Figs.  2  and  3)  consists  of  one  or  more  grooved  pulleys 
or  sheaves  turning  on  an  axle,  called  a  pin,  mounted  in  a  casing  or 
shell,  which  is  furnished  with  a  hook,  eye  or  strap  on  one  end,  by 
which  the  block  may  be  attached  to  something  and  sometimes 
with  a  l)ecket  on  the  other  end  for  attaching  ropes,  etc.  It  is  used 
to  transmit  power,  or  change  direction  of  motion,  by  means  of  a 
rope  or  chain  passing  round  the  movaV)le  pulleys.  Blocks  are 
single.  dou])le,  treble,  or  fourfold,  according  as  the  number  of 
sheaves  oi-  jjiillcys  is  one,  two,  three  or  four.      The  size  of  blocks 


142  Use  op  Cordage  and  Spars. 

is  expressed  by  the  length  of  the  shell  in  inches.  A  common  style 
of  Ferry  Block  is  shown  in  Fig.  5. 

A  snatch  block  (Fig.  4)  is  a  single  block  with  a  notch  cut  in  one 
cheek  so  as  to  receive  the  standing  part  of  a  fall  without  the 
trouble  of  reeving  and  unreeving  the  whole. 

A  riuming  block  is  one  attached  directly  or  indh*ectly  to  the 
object  to  be  raised  or  moved ;  a  standing  block  is  one  fixed  to 
some  permanent  support. 

229.  xl  tackle  consists  of-e»€  or  more  blocks  with  a  rope  rove 
through  them  for  use  in  hoisting. 

230. — The  parts  of  all  ropes  between  the  points  of  fastening 
and  sheaves  are  called  standing  parts;  the  parts  between  the 
sheaves  are  called  running  parts ;  the  part  to  which  the  power  is 
applied  is  called  the  fall. 

231. — To  overhaul  di  tackle  is  to  separate  the  blocks;  to  round 
in  is  to  bring  the  blocks  closer  together. 

A  tackle  is  said  to  be  block  and  block  or  two  blocks  when  the 
entire  fall  is  hauled  through  so  the  blocks  are  in  contact. 

232. — Before  reeving  a  rope  in  a  block,  it  should  be  stretched 
out  its  full  length.  Tackle  should  not  be  allowed  to  twist;  to 
prevent  it,  insert  a  bar  in  the  block  or  between  the  running  parts 
and  use  it  as  a  lever  to  hold  straight.  If  allowed  to  make  one 
complete  turn  with  2  single  blocks,  the  friction  will  increase  the 
resistance  about  40^.  Ropes  should  not  be  too  large  for  blocks, 
the  rule  being,  ^^ Small  i^opes  ami  (>/'(/  hJocks:' 

233.— PoAver  of  Tackle.  Theoretically,  the  power  neces- 
sary to  just  balance  a  weight,  with  a  tackle  of  two  blocks,  is 
equal  to  the  weight  divided  by  the  number  of  ropes  at  the  run- 
ning block. 

234. — To  produce  motion,  however,  a  greater  power  is  required 
to  overcome  friction  and  stiffness  of  rope.  It  has  been  found  by 
experiment  that  to  do  this  about  10%  of  the  theoretical  power 
necessary  to  balance  must  be  added  to  itself  for  each  of  the 
sheaves  over  which  the  rope  passes,  the  blocks  being  in  good  con- 
dition and  well  oiled.  If  not  in  good  condition  and  not  well  oiled, 
the  per  cent  may  be  as  high  as  30  for  each  sheave. 

235. — The  formula  P  =r  ^^^'^  is  used  to  determine  the  power 
required  to  raise  a  weight  with  a  simple  tackle,  in  which  P  =  the 
powder  required ;  W  =:  the  weight  to  be  raised,  S  =  the  number 


PLATE  33. 


/'i'p/d  /'h/'.y/r//i 


i^'-nrv"f 


Pta 


a 


Sectiork 


w/^^J^ 


v7rr,y^y!j}f 


^/1 


Use  ok  Cokdacje  and  Spars.  145 

of  sheaves,  and  K,  =  the  number  of  ropes  tit  running  block,  in- 
cluding standing  part  if  attached  to  it.  If  it  is  required  to  find 
how  great  a  weight  a  certain  power  will  lift  the  formula  is 
W  =  -^.  Power  is  gained  only  at  the  loss  of  time.  The  power 
moves  as  many  times  faster  and  farther  than  the  weight  as  the 
number  of  ropes  at  the  running  block.  No  advantage  is  gained 
by  using,  in  one  fall,  a  greater  number  of  sheaves  than  two  treble 
blocks,  but  may  be  by  a  combination  of  blocks  and  tackles. 

236. — A  squad  of  men  hauling  on  a  fall  exert  a  jjull  of  about 
80  lbs,,  or  half  their  weight  each,  the  fall  being  nearly  horizontal. 

237. — A  Derrick  (Fig.  7)  usually  consists  of  a  single  spar 
or  leg,  held  up  by  4  guys,  and  having  a  tackle  lashed  to  the  top, 
used  for  hoisting  or  lowering  heavy  bodies  within  a  circle  whose 
diameter  equals  the  height  of  the  spar.  When  made  of  2  legs 
(Fig.  8)  they  are  mortised  into  a  cap  on  top  and  a  sill  at  the  bot- 
tom, only  two  guys  being  required,  a  fore  and  back,  but  three  are 
better,  one  fore  and  two  back.  The  weight  can  only  swing  be- 
tween the  legs.  The  holdfasts  for  the  guys  should  be  at  a  dis- 
tance from  foot  of  derrick  at  least  twice  its  height.  The  foot 
should  be  secured  from  slipping  by  being  let  into  a  hole  in  the 
ground  or  otherwise. 

238.— Sliears  (PI.  33,  Fig.  1)  consist  of  two  spars,  of  a  size 
suitable  for  the  weight  to  be  raised,  lashed  together  at  the  cross. 

A  tackle  is  fastened  at  the  lashing  by  a  strap  passed  around  it 
or  otherwise,  the  hook  moused,  and  holdfasts  are  required  as  for 
two-legged  derrick. 

Derricks  and  shears  should  not  lean  to  exceed  }^  of  their 
height  and  each  leg  should  have  about  ^4  this  inclination. 

239.— A  Gill  (Fig.  2)  is  a  tripod  formed  of  three  poles.  The 
two  outside  ones  are  called  legs,  the  third  one  the  jn-y  pole.  Gins 
require  no  guys.     Weights  can  only  be  lifted  vertically. 

240. — In  using  derricks,  shears,  and  gins,  the  h\\\  is  generally 
led  through  a  snatch  })lock  lashed  on  a  leg  near  the  bottom,  thence 
to  a  crab,  windlass,  or  capstan.  Derricks  frequently  have  fas- 
tened on  their  legs  (/  winch  for  transmitting  the  power.  (PI.  32, 
Fig.  10.) 

2-1-1. — A  Windlass  (Fig.  12)  consists  of  a  horizontal  axis 
fastened  in  a  frame  and  turned  l)y  means  of  cranks  or  handles. 
The  n)])e  may  cither  be  fjistcned  to  the  axis  or  passed  two  or  tliree 


140  Usi:    OV    roiJDAflE    AND    SlWKS. 

times  around  it,  hauled  tiiut,  the  free  end  being  held,  and  taken  in 
by  men  in  the  rear. 

242.— A  Capstan  (Pi.  32,  Fig.  9,  and  PL  33,  Fig.  3,)  consists 
of  an  upright  barrel,  either  smooth  or  ribbed,  arranged  about  a 
spindle.  Above  the  barrel  is  the  head  with  holes  to  Teceive  the 
ends  of  levers  or  bars  by  which  the  barrel  is  revolved.  The  rope 
is  passed  and  held  as  explained  for  a  windlass. 

243. — Holdfasts  are  stout  wooden  stakes  driven  into  the 
ground,  or  oilier  ;ii  ranj^ements  used  for  securing  purposes. 

An  essential  ]K>int  to  be  considered  before  moving  or  suspend- 
ing heavy  weights  is  the  nature  and  condition  of  the  securing 
points,  together  with  the  strain  that  will  be  brought  upon  them. 
In  the  first  instance,  it  is  better  to  make  them  more  secure  than 
seems  to  be  absolutely  necessary,  as,  when  they  once  begin  to  give 
way,  it  is  difficult  to  strengthen  them.  PI.  33,  Figs.  4,  5,  6  and  7, 
show  some  of  the  various  methods  of  making  them,  also  PI.  40a. 


PLATE  34. 


^  w    The  f 

UNIVEK8ITY 
ClIAPTEK  XV.     Spar  Brid^^os. 


li-A-i. — Mililary  Bridg-es  are  not  required  to  fultil  all  the 
conditions  of  ordinary  bridges.  They  are  constructed  for  special 
and  immediate  purposes,  usually  with  unskilled  labor,  and  of 
such  materials  as  can  be  procured  on  or  near  the  spot.  That  the 
bridge  built  shall  be  strong  enough  to  bear  the  heaviest  load  in- 
tended to  be  crossed  is  the  first  requisite;  celerity  and  siniijlicity 
of  construction  next. 

245. — PL  34  is  an  illustration  of  what  was  done  in  building 
Military  Railroad  Bridges  under  unfavorable  circumstances  in 
time  of  war  with  troojjs  of  the  line,  very  few  of  whom  were  me- 
chanics, many  could  not  even  handle  an  ax,  none  were  trained  to 
the  duty,  and  none  were  engineer  troops.  This  bridge  was  built 
by  General  Haupt  over  Potomac  Creek,  Va.  ,during  the  Rebellion, 
and  was  80  ft.  high  and  iOO  ft.  long.  It  consisted  of  three  tiers  of 
trestles  on  top  of  cribs  12  ft.  high.  The  timber  used  was  chiefly 
round  sticks,  cut  in  the  woods  near  by,  and  put  together  without 
bolts,  simply  with  spikes  and  wooden  pins,  and,  when  finished, 
was  crossed  by  10  to  20  heavily  loaded  trains  per  day.  This  kind 
of  work,  however,  properly  belongs  to  a  special  construction  corps, 
but  it  falls  to  the  lot  of  the  officers  and  men  who  first  arrive  at  a 
stream  on  the  ordinary  roads,  where  there  are  no  means  of  cross- 
ing, to  construct  ^n  improvised  bridge  with  such  tools  and  of  such 
materials  as  may  be  available. 

24:G. — The  jjlans  and  expedients  which  follow  have  been 
selected  with  a  view  to  their  being  types  of  bridges  that  can  be 
ccmstructed  by  troops  having  no  other  tools  than  axes  and  augers, 
and  such  materials  as  growing  trees  found  in  the  vicinity,  and 
beams,  boards,  ropes,  wire,  nails,  etc.,  obtained  from  neighboring 
houses  and  towns.  The  i^urposes  for  which  the  bridge  is  to  be 
used,  the  nature  of  the  crossing,  velocity  of  stream,  and  kind  of 
bottom,  will  determine  its  strength,  kind,  size,  etc. 


150  Si'Ai:  Ukijj(,ks. 

247.— Foi-  a  coiiinion  road  bridge,  the  load  is  assumed  to  be  a 
maximum  when  covered  with  men,  estimated  at  120  lbs.  to  the 
sq.  ft.,  pins  the  woi<,4it  of  the  bridge,  usually  taken  at  about  80 
lbs.  per  lineal  It.  For  reasons  which  are  evident,  the  bridge 
should  be  as  sliort  as  possible,  with  good  approaches.  Swampy, 
high,  or  steep  banks  should  be  avoided. 

248. — Bridges  usually  take  their  names  from  some  part  of  their 
construction,  as  Treatle,  Truss,  Pile,  Suspension,  or  Floating 
Bridges.  The  distance  between  supports  (determined  by  the 
strength  of  the  balks  to  bear  the  desired  load)  is  called  the  hay  or 
span,  and  the  corresponding  part  of  the  bridge  the  span.  The 
superstrffcfKrc,  consisting  of  the  stringers  or  balks,  the  floor,  the 
side-rails  and  the  fastenings,  is  of  the  same  nature  for  each  kind, 
as  shown  in  PI.  35,  Fig.  1.  The  ends  of  the  balks  rest  on  cross 
I^ieces  of  the  supports  called  transoms,  on  the  balks  (of  which 
there  are  usually  five)  are  laid  chess  or  poles,  forming  the  floor  ; 
on  top  of  the  floor,  over  the  outside  balks,  are  laid  side-rails  or 
poles,  which  are  securely  fastened  every  4  or  5  ft.  to  the  balks  be- 
neath by  rack  lashings.  Hand-rails  (Fig.  2)  should  always  be 
provided  on  each  side  of  the  roadway.  The  usual  width  of  mili- 
tary bridges  is  9  ft.  in  the  clear,  between  side-rails;  6  ft.  will 
answer  for  Infantry  in  column  of  two's,  and  Cavalry  by  file  ;  2.5  ft. 
for  Infantry  in  single  file. 

249. — For  determining  the  strength  of  the  materials  to  be 
used,  all  errors  should  be  on  the  side  of  safety.  The  practical 
method  is  to  place  the  ends  of  the  timber  on  low  supports,  as  far 
apart  as  they  will  be  in  bridge;  as  many  men  as  can,  then  step 
on  it  and  jump  up  and  down ;  or  it  is  otherwise  arranged  so  as  to 
bring  as  great  a  weight  upon  it  as  it  will  have  to  bear  at  any  time 
in  bridge. 

Where  small  poles  of  the  usual  number  would  not  be  strong 
enough,  a  greater  number  must  be  used  until  the  desired  strength 
is  gained. 

250. — Transoms  must  be  strong  enough  to  bear  all  the  weight 
that  may  be  brought  upon  one  bay  of  the  bridge,  considered  as 
distributed  dead  load  on  the  transom. 

261,— The  load  in  pounds  which  any  timber  resting  on  two 
points  of  support  will  safely  bear,  concentrated  at  its  center,  may 

bd^ 
be   approximately  determined    by  the   formula   ^  x  -p-    x  C,  in 


PLATE  35. 


Of  Tue    ^n 

'FORM  I  A. 


Spak  Bkidces.  153 

which  b  ~  the  breadth  in  inches,  d  1=:  the  depth  in  inches,  1  = 
the  length  in  feet  between  supports,  and  C  is  a  constant  in 
pounds  for  the  particular  material  of  the  beam  *  *  is  the  frac- 
tion of  the  breaking  weight  used  for  safety.  It  would,  in  all 
cases,  bo  better  to  use  a  smaller  fraction  of  the  breaking  weight, 
as  i  or  i;  or  even  |  in  cases  of  importance  or  of  a  permanent 
character.  The  formula  is  for  a  rectangular  beam,  but  for  a 
cylindrical  timber  whose  mean  diameter  equals  the  side  of  a 
square  beam,  use  ^^o  of  what  the  formula  gives. 

2 o'2,— Weight  brought  on  a  bridge  by  the  passage  of  troops^ 
taken  as  distributed  live  load  for  Infantry  and  Cavalry  :  Infantry 
in  column  of  twos  or  fours  about  225  lbs.  per  lineal  foot.  In- 
fantry when  crowded  at  a  check  in  fours  about  550  lbs.  per  lineal 
foot.  Cavalry  in  column  of  twos  about  230  lbs.  per  lineal  foot. 
Cavalry  when  crowded  at  a  check  about  350  lbs.  per  lineal  foot. 
When  Artillery  carriages  cross  a  bridge,  the  weight  is  not  equally 
distributed,  bat  in  greatest  when  the  ivheeh  bearing  the  heaviest 
load  ((re  on  tlic  center. 

25:J.  A  uniformly  distributed  dead  load  produces  only  one- 
half  the  strain  of  an  equal  dead  load  concentrated  at  the  center. 
A  moving  or  live  load  produces  twice  the  strain  of  a  dead  load. 
A  uniformly  distributed  live  load  equals  a  concentrated  dead  load. 

Table  of  Constants,  C,  for  finding  the  breaking  load  of  various 

bd2 
materials  by  the  formula  I  x  -y-  x  C  when  concentrated  at  cen- 
ter of  beam  supported  at  both  ends.    From  "Trautwine's  Engi- 
neer Pocket  Book  :" 

Ash,  white. ...  650    Elm 350    Oak,  red  and  black  550 

Ash,  swamp. . .  400    Hemlock 400    Pine,  white 450 

Ash,  black ....  300    Hickory 700    Pine,  yellow 500 

Beech,  white.  .450    Hickory,  pig  nut.  .500    Pine,  pitch 550 

Beech,red 550    Locust 600    Poplar 550 

Birch 450    Mahogany 450    Spruce 450 

Cedar 250    Maple 550    Sycamore 500 

Chestnut 450    Oak,  white  and  live  600    Walnut 450 


*U  is  deterniined  by  taking  a  piece  1  in.  square,  and  1  ft.  long  between  supports,  load- 
ing it  at  the  center  until  it  breaks,  then  to  the  applied. load  adding  one-ha^f  the  weight 
of  the  piece  between  supports,  and  the  sura  will  be  C  ;  or,  a  piece  of  any  convenient  size 
and  length  can  be  used,  afterwards  deducing  what  the  breaking  weight  would  be  for  a 
piece  1  in.  square  and  1  ft.  long,  remembering  that  the  breaking  weight  varies  directly 
with  the  width,  as  the  square  of  the  depth,  and  inversely  as  the  length. 


'•''  Si'\i:    I  Jk'i  i)(,i:s, 

254.  77/(^  ('((hie  contents  of  a  log^  is  approximately  equal  to 
0.7854  times  the  square  of  the  mean  diameter  times  the  length,  or 
the  area  of  the  mean  section  multiplied  liy  the  length;  or  the 
square  of  one-tifth  the  mrjin  circiiinfc^-cncc  times  twice  the 
length,  all  in  feet. 

255.  In  calculating  the  strength  of  a  round  timber  or  spar, 
its  mean  diameter  is  used,  because  such  a  spar,  if  overloaded,  will 
break  at  center,  instead  of  at  small  end.* 

25(>.  The  following  ta))l('  ui\cs  the  w.-iuhts  in  lbs.  prv  cu.  ft. 
of  various  materials: 

Chestnut 40    Spruce ;U 

Cottonwood 35    Sycamore 37 

Hickory 43-49    Walnut 38 

Maple 48    Clay 120 

Oak 45  GO    Earth 71M20 

Pine. 34  40  Gravel  &  sand.90  130 

from  I  to  J  more  than  those  in  table. 

257.  WIk'ji  sjinrs  jiic  used  for  balks,  they  nnist  ])e  arranged 
so  as  to  have  all  butts  ov  all  tips  together  on  a  transom.  They 
should  have  good  overlap  and  be  well  lashed  to  each  other  and 
the  transoms.  To  allow  for  settling,  the  centre  is  generally  made 
higher  by  about  3',,  tlic  span. 


Iron,  cast 

\vi-ou,u-ht   . 
Lead 

...450 

...487 
.. .710 

Steel 

. ..188 

Ash 

:\s  47 

Cedar 

....,35 

■  K.T  a  hridjjTo  constructed  as  in  Kig.  '^,  witli  (>  lialk-^,  tn  (Ict.riniiic  the  ^.itC  1();m1  it  will 
(■an,\  .  ilif  aiip  icatioM  will  be  about  as  follows: 

The  balks  heinj?  of  yellow  pine,  10  inches  in  diameter  at  the  center,  25  ft.  between  sup- 
f,         1  103 

.    ports,  the  fornuila  jrivts    ^o    ^   ;V    "^     2.5    ^  ^^  =  ^.^^  ^bs.  as  the    safe  load  each  balk 

will  bear  concentrated  at  the  center,  including  its  own  weight.  Calculating  for  5  balks« 
on  the  supposition  that  the  two  out5<ide  ones  receive  only  M  the  strain  of  the  center 
ones,  they  will  bear  5  x  4,000  lbs.  =  20,000  lbs.  concentrate  1  at  center.  From  this  deduct 
half  the  weight  of  the  balks  and  floor  concentrated  at  centei-,  found  ])y  multiplying  M 
the  cubic  contents  by  the  weight  per  lb  :  for  the  (>  balks  this  will  be 

6  X  I   r  /  5\2  X  .7854  1  X  25  X  40  =  1636.25  lbs. 
For  the  floor  of  50,  4-in.  poles,  each  12  ft.  long,  the  weight  will  be 

.^0  X  I  X  r  (1)'  X   .78.">4  1  X  12  X  40  =  1047.24  lbs. 
2(l,(M)0  lbs.  —  •,'  tlS.S  .')  lbs.  =  17  :516.:>  lbs.,  the  capacity  of  the  bridge  concentrated  at  the  cen- 
t.i'.     Infaiitiy  inanliing  in  column  of  fours  crowded  by  a  check  would  cause  a  load  of 
only  about  i:'.  T.M)    lbs.      (\ivalry  in  column  of  twos  crowded   by  a  check  only  about  8,750- 
lbs. 

Similarly,  knowing  the  siian  the  kind  of  material  at  hand,  the  weight  to  be  borne, 
etc.,  the  size  of  timbers  rcciuird  can  be  deduced;  oi,  having  the  size  and  kind  of  the 
timbers,  weight  to  be  borne,  etc  ,  the  greatest  length  that  can  be  spanned  can  be  deter- 
mined by  the  above  formula 

Foot  nt)te  pg.  154,  for  ''lb '' read  '-ft."  \veight  of  floor  deduced  for   50     . 
poles  siiould  be  for  75.  ^-^<*.^^ 


REESe  ^/ 


PLATE  36. 


FIG.l. 


PIG.  2. 


FIG.3. 


Spar  Bridges.  15T 

258.— i^or  spans  of  25  feet  or  less,  if  timber  is  available,  the 
simplest  form  of  stringer  bridge  could  be  built,  as  in  Fig.  2,  of  6 
balks,  30  ft.  long,  reaching  clear  across,  covered  with  small  poles 
4  to  6  in.  in  diameter,  12  ft.  long,  for  a  floor.  Side -rails  would  be 
laid  on  the  floor  over  the  outside  balks  and  either  lashed  or 
pinned  to  the  balks.  Hand-rails  would  be  as  shown  or  a  rope 
stretched  across  would  answer.  Time  of  construction — 1  hour. 
The  balks  could  be  jumped  across  as  shown  in  either  Figs.  3  or  4. 

259. — If  stringers  of  length  to  reach  across  cannot  be  obtained 
or  are  too  heavy  to  handle  easily,  a  bridge  as  in  Fig.  5  might  be 
made,  requiring  only  axes  and  augers.  The  shore  stringers,  25  ft. 
long,  10  in,  in  diameter,  six  on  each  shore,  have  their  bridge  ends 
scarped  on  upper  side  18  in.,  then  pushed  out  10  ft.,  their  shore 
ends  being  well  anchored  down  and  loaded  with  roadway.  Six 
short  stringers,  8  ft.  long,  10  in.  in  diameter,  three  on  each  shore, 
scarped  18  in.  on  under  side  of  each  end  are  passed  orer  gap  and 
laid  on  shore  stringers.  Two  2-in.  auger  holes  are  bored  at  each 
end  through  both  stringers  and  wooden  pins  driven  through,  and 
the  flooring  completed. 

260. — Paiiie's  Bridge.  (Fig.  6.)  If  timber  is  abundant  and 
stream  not  over  6  ft.  deep,  select  trees  up  stream.  Fell,  and  trim 
off  branches.  Bore  two  3-in.  auger  holes  near  butt  ends  3  in. 
apart,  making  an  angle  of  30°  with  each  other,  and  a  third  hole, 
making  an  angle  of  45°,  between  them  nearer  the  butt.  Cut  and 
insert  in  outside  holes  legs  long  enough  to  raise  the  butt  the  de- 
sired height  of  bridge.  Float  down  stream,  butt  end  first,  to  posi- 
tion of  bridge.  On  arriving  in  line  of  bridge,  the  log  is  turned  on 
its  feet,  the  tip  sinking  to  bottom.  The  brace  leg  is  then  inserted 
down  strea'm  in  last  hole  making  an  angle  of  45°.  Log  after  log 
is  thus  placed,  balks  rolled  up  and  put  into  i30sition  and  leveled 
and  the  floor  laid  in  the  usual  way. 

201. — For  spans  of  25  ft.  or  over,  when  bottom  can  be  touched 
clear  across,  some  form  of  trestle  bridge  will  be  the  easiest  of  con- 
struction. 

202.— In  PL  36,  Fig.  1,  the  trestle  consists  of  6  legs,  4  vertical 
and  2  inclined ;  the  two  vertical  legs  on  each  side  are  fastened  to 
two  short  sills  by  2-in.  pins.  The  ends  of  the  two  inclined  legs 
are  cut  on  an  angle,  driven  into  position  and  held  by  2-in.  pins 
passing  through  the  transom  from  above.  Theyserve  as  braces 
and  supports.     A  short  horizontal  piece  pinned  to  each  pair  of 


158  SpAii  Bii]i)(ii<>'. 

vertical  legs  sui)ports  the  transom,  which  is  also  pinned.  On  top 
of  the  projecting  ends  of  the  vertical  legs  a  cap  piece  can  be 
pinned  to  form  hand-rails.  The  trestle  is  made  on  shore,  floated  to 
its  place  in  bridge,  and  erected  with  the  aid  of  a  float  held  at  the 
proper  distance  from  last  trestle  by  a  pole  on  each  side,  having 
the  lengths  of  the  sp^ins  marked  by  pins  which  engage  the  tran- 
soms of  the  trestles.  The  transoms  are  only  temporarily  lashed 
in  position  at  first,  but  after  the  trestle  is  erected  in  its  proper 
place  the  proper  height  for  it  is  determined  by  bringing  the  2 
distance  poles  horizontal,  or  a  little  above  the  horizontal  if  a  cam- 
ber is  to  be  given,  then  pinning  or  spiking  on  the  short  horizontal 
pieces.  If  accurate  soundings  have  been  made  across  the  stream 
on  the  lines  of  the  legs  of  the  trestles,  then  the  trestles  can  be 
completed  on  shore  before  launching.  The  balks  are  then  run 
across  and  pinned  and  roadway  finished.  If  there  occurs  unequal 
settling,  the  roadway  can  be  raised  by  blocking  up  under  the  tran- 
soms on  the  short  horizontal  pieces. 

2()8.  Fig.  2  is  another  form  of  trestle  (ailed  the  Tio-block 
Trestle,  consisting  of  only  two  legs,  about  8  in.  in  diameter. 
The  transoms  are  in  pairs,  across  which  two  blocks  are  spiked  at 
each  end  into  notches,  as  shown.  This  trestle  can  be  used  on 
hard,  uneven  bottom.  The  trestle  is  formed  on  shore,  held  in 
shape  by  the  rope,  and  rack  stick  across  the  top,  then  floated  into 
place.  Two  poles,  longer  than  two  spans,  are  then  run  out;  on  the 
projecting  ends  are  pins  to  prevent  tlie  trestle  slipping  otf,  and  on 
near  end  a  rope  for  fastening  to  transoms  of  second  trestle  back. 
Having  caught  the  trestle  on  the  ends  of  the  poles  under  the  tran- 
som, it  can  be  raised  to  a  vertical  position  by  men  bearing  down 
on  the  rear,  and  held  by  means  of  ropes ;  it  is  then  lowered  into 
position,  legs  in  a  vertical  plane.  The  transoms  are  then  adjusted 
to  their  proper  elevation  by  striking  on  under  side,  if  too  low,  then 
tightening  rope;  or  by  slackening  the  rope  and  striking  on  upper 
side  if  too  high.  When  properly  adjusted,  the  rope  is  tightened, 
pinching  the  legs  between  the  blocks ;  the  braces  are  then  spiked 
or  pinned  on,  the  rope  removed,  the  balks  laid  and  pinned,  and  the 
poles  shoved  out  for  the  next  trestle. 

264. — Where  sufficient  lumber  can  be  procured,  the  most  ex- 
peditious and  probably  the  best  method  will  be  as  follows  :  (Fig. 
3.)  With  the  balks  and  chesses  for  each  span,  form  a  raft,  or  as 
many  as  may  be  desired,  the  length  of  a  span.    Form  a  trestle  by 


Spar  Buiikjks.  159 

placing  4  legs  parallel  and  4  ft.  apart  from  center  to  center.  Spike 
a  pole  across  near  the  bottom  and  one  near  the  top  to  keep  them 
together.  The  first,  or  any  trestle,  having  been  set,  float  a  raft 
against  it  and  make  fast ;  bring  the  trestle  to  be  set  up  to  the 
other  end ;  force  the  legs  under  the  raft  a  distance  a  little  less  than 
the  depth  of  the  water.  Tie  a  rope  around  the  outside  legs  at 
"f "  with  a  bow-knot,  to  hold  from  slipping  under,  and  others  to 
the  top  pole,  by  means  of  which  it  is  raised  to  a  vertical  position 
when  it  is  dropped  to  the  bottom  by  slackening  off  on  lower  ropes. 
As  soon  as  it  is  dropped,  another  raft  is  brought  up,  tied,  and  an- 
other trestle  put  into  position,  and  so  continued.  Each  trestle,  as 
soon  as  it  is  in  position,  is  then  capped  by  nailing  two  boards  hor- 
izontally on  opposite  sides  of  legs  with  tops  in  same  plane.  (Fig. 
3,  a.)  Braces  are  then  spiked  on  the  legs.  Saw  off  the  two  inside 
posts  even  with  the  tops  of  boards.  Spike  a  2-in.  plank  across  the 
top  of  posts  and  boards.  Lay  the  balks,  spike  them,  remove  the 
raft,  and  move  it  into  position  to  raise  another  trestle.  If  boards 
cannot  be  procured  for  capping,  round  sticks  may  be  used  as  in 
Pig.  3,  b,  by  cutting  the  two  inside  legs  off  5  or  6  in.  above  the 
horizontal  poles,  then  spiking  two  short  pieces  across  the  poles 
against  the  outside  legs  and  one  in  center  on  which  the  cap  piece 
or  transom  will  rest.  Advantages  are — work  can  be  commenced  in 
any  number  of  places  at  the  same  time;  no  accurate  soundings 
required  so  long  as  poles  are  sufficiently  long ;  capping  and  bracing 
do  not  retard  work ;  different  squads  can  be  at  work  at  same  time, 
etc. 

265. — If  only  axes  and  rope  are  available,  trestles  may  be  made 
by  lashing  their  parts  together.  Pig.  4  shows  the  Two-legged 
Trestle.  Having  determined  the  height  of  the  roadway  above 
the  bottom  of  the  stream,  mark  this  height  from  the  butts  on  both 
legs,  then  mark  the  position  of  the  transom  on  the  legs,  allowing 
for  the  thickness  of  the  balks ;  also  mark  on  the  transom  for  the 
width  of  roadway  between  side-rails  plus  3  ft.,  for  points  of  cross- 
ing of  legs,  the  distance  apart  of  legs  depending  on  width  of 
roadway.  Give  the  legs  a  splay  outwards  at  the  bottom  of  ^  and 
mark  on  legs  and  ledger  the  points  of  lashing.  All  being  ready, 
lay  the  transom  on  a  couple  of  supports  3  or  4  in.  high,  inside  the 
position  of  the  legs,  lay  oa  the  legs  in  their  proper  positions,  on 
the  legs  lay  the  ledger.  With  the  square  lashing  fasten  the  four 
points  of  crossing.     Next,  lay  on  the  braces,  butts  and  one  tip  on 


I'J*'  Si'AK     l>KI  l)(,KS. 

same  side  as  leilger  and  one  ti^j  on  side  of  transom.  Lash  the 
butts  with  square  lashings.  Square  the  trestle  by  making  the 
diagonals  equal,  measuring  from  the  centre  of  ledger  lashing  on 
one  leg  to  the  centre  of  transom  lashing  on  opposite  leg.  When 
these  diagonals  are  made  equal  the  tips  are  lashed  with  square 
lashings  and  the  braces  at  the  middle  with  a  cross  lashing.  Led- 
ger and  braces  can  be  of  rather  light  timber.  The  trestles  can  be 
floated  into  position  and  raised  as  already  described,  or  run  out 
and  down  from  the  end  of  the  bridge,  which  is  more  difficult. 
They  are  kept  vertical  by  lashing  the  balks  to  tlie  transoms,  and 
longitudinal  bracing  from  one  to  another. 

26().  A  Tliree-legged  Trestle  (PL  37,  Fig.  1)  may  be 
made  by  first  lashing  two  legs  together  considerably  higher  than 
the  roadway  is  to  be,  then  lashing  the  pry-pole  just  below  to  one 
of  the  legs,  all  with  shear  lashings.  Stand  the  trestle  up,  spread 
out  legs  till  butts  rest  on  the  vertices  of  an  equilateral  triangle 
whose  sides  are  J  height  of  trestle,  then  lash  three  light 
ledgers  to  the  legs  by  round  lashings.  On  the  outside  of  the  pry- 
pole  and  leg  to  which  it  is  fastened  are  lashed  short  pieces,  by 
square  lashings,  on  which  rest  two  longer  pieces,  separated  by  the 
legs,  which  are  lashed  together  by  the  shear  lashing.  On  these 
longer  pieces  rest  the  transoms.  With  these  trestles  lighter  ma- 
terial can  be  used ;  they  stand  without  bracing  but  are  difficult  to 
place;  accommodate  themselves  to  inequalities  of  surface;  the 
roadway  may  be  readily  raised  or  lowered.  If  material  is  avail- 
able, they  are  readily  made  with  spikes. 

267. — Fig.  2  is  another  form  of  trestle  of  four  legs.  Two  two- 
legged  trestles  are  made,  one  being  12  to  18  in.  narrower  than  the 
other,  depending  on  the  size  of  legs,  S3  that  they  will  lock  when 
put  together.  The  transoms  are  placed  on  same  side  as  ledgers, 
instead  of  on  opposite  sides.  The  butts  of  the  single  trestles  are 
I)laced  a  distance  apart  equal  to  half  the  height,  then  locked  at  the 
top,  the  transoms  lashed  at  the  ends,  longitudinal  braces  lashed  at 
the  ledgers,  the  tips  tied  and  racked  together.  Sometimes  used 
with  light  material,  also  as  steadying  points  in  a  long  bridge  of 
two  legged  trestles.  One  similar  to  it  can  l)e  made  of  sawed  tiiii 
ber  and  spikes  and  jjlaced  in  position  as  shown  in  Figs.  3  and  1,  if 
the  materials  are  available. 

268. — In  sluggish  streams  with  muddy  bottoms  and  not  owv  C) 
ft.  deep,  where  timber  is  abundant,  crib  piers  may  be  used.     (Fig. 


PLATE  37 


PLATE  38. 


UNIVLKSITl 
FIG.  4.   S/nn/r  I.orA'  .   ^vC4L|F0RN\^  . 


JA^ 


Sf'Ai:  13i:ji)(iES.  165 

5.)  The  cribs  are  built  in  the  woods,  the  foundation  lo^s  bein^ 
Xjinned  together,  the  others  simply  notched.  The  logs  are  then 
marked,  taken  down,  carried  or  floated  into  position,  and  re- 
built, poles  being  generally  set  to  mark  the  corners.  As  the  crib 
is  built  up  it  gradually  sinks,  or  a  tray  may  be  formed  inside  and 
loaded  with  stones.    The  balks  and  flooring  are  laid  as  usual. 

209. — Pile  bridges  are  scarcely  adapted  to  an  emergency,  from 
the  time  and  preparation  required  in  their  construction,  but  on 
linos  of  communication,  from  the  character  of  the  bottom  or  the 
dangers  from  floating  objects,  resort  may  be  had  to  them. 

2  TO. — For  driving  the  piles,  a  monkey  (Fig.  8)  is  made  of  a 
block  of  wood  3  ft.  long,  12  in.  in  diameter,  with  four  1.5  in.  i)ins 
at  top  and  four  on  the  sides  for  handles.  Four  men  standing  on 
a  platform  on  the  pile  drive  it  down,  their  own  weight  thus  assist- 
ing, or  they  maybe  driven  from  a  raft  built  as  in  Fig.  6.  After  the 
piles  are  driven  they  are  straightened,  braced,  their  tops  sawed  off 
level,  the  caps  i)laced  on  and  pinned  (PI.  38,  Fig.  1),  and  the  roadway 
laid  as  usual.    Piles  near  shore  may  be  driven  as  in  Fig.  7. 

271. — For  crossings  greater  than  25  ft.  and  too  deep  to  use  any 
of  tlie  above  forms,  resort  must  be  had  to  some  form  of  t)-uss 
bridcjc.  The  trusses  may  be  put  together  either  by  lashing  or  with 
pins,  or  by  combinations  of  both. 

272. — PI.  38,  Fig.  2,  rejjresents  the  ordinary  Kiiig'-post 
Truss  for  spans  up  to  40  ft.  The  bridge  is  imt  together  on  the 
bank,  then  pushed  forward  halt*  its  length,  using  rollers  under 
ea-ch  truss,  as  shown.  A  trestle  is  then  leaned  forward  from  oppo- 
site bank,  and,  when  truss  is  over  it,  the  trestle  is  raised  and  the 
end  of  the  truss  carried  over  to  the  opposite  bank. 

273. — Fig.  3  represents  the  Qiieeii-iiost  Truss  for  spans  up 
to  50  ft.  It  is  constructed  and  carried  across  similar  to  the  pre- 
ceding one. 

274.- Fig.  4  shows  the  Siiigle-I^ock  for  spans  of  30  ft.  It 
consists  of  two  frames  similar  to  the  two-legged  trestle  on  PI.  36, 
Fig.  4.  A  section  of  the  gap  is  first  marked  out  on  the  ground  on 
each  bank  with  the  positions  of  the  footings  indicated.  On  these 
the  legs  are  laid  and  the  positions  for  lashing  the  transoms  and 
ledgers  marked.  The  frames  are  then  put  together  opposite  the 
I^osition  they  are  to  occupy  (one  on  each  bank),  butts  towards  the 
gap.  One  frame  is  made  15  to  18  in.  wider  than  the  other  so  they 
will  lock,  and  the  footings  should  be  likewise  prepared.    The  dis- 


H>t>  Siwii  Bi;iik;ks. 

tance between  Icj^sat  traiisoiuof  nari-ower  rraiuc  is  18  in.  more  than 
width  of  roadway  between  side-rails.  With  the  above  exceptions 
the  frames  are  made  like  the  two-legged  trestles.  The  splay  of 
the  legs  is  very  slight,  generally  about  1  ft.  between  transom  and 
ledger.  Stout  stakes  are  then  driven  at  the  rear,  fore  and  back 
guys  are  attached  to  the  tips  of  each  frame,  the  fore  guys  crossed 
over  the  stream,  those  of  narrower  frame  in  center.  Foot  ropes 
are  also  attached  to  each  leg  near  the  butts  with  timber  hitches 
and  a  turn  taken  around  the  stakes  at  the  rear.  The  frames  are 
then  shoved  over  the  banks  till  they  balance  (PI.  40,  Pig.  1)  then 
brought  to  a  vertical  position  by  hauling  on  the  fore  guys,  and 
lowered  into  their  places  by  easing  off  on  the  foot  ropes,  after 
which  they  are  pulled  over  and  locked.  A  couple  of  balks  are 
then  run  out,  then  the  fork  transom  is  put  into  place  and  the 
balks  rested  on  it.  The  remainder  of  the  balks  are  then  run  out, 
placed  on  the  fork  transom,  lashed,  and  the  roadway  completed  as 
usual.  If  good  places  for  footings  cannot  be  secured,  then  other 
means  must  be  provided. 

275.— For  spans  up  to  i'>  or  '>(>  fl..  i\\v  Doiible-Tjock  (PI. 
39,  Fig.  1)  may  be  used.  In  this  it  will  be  noticed  that  the  balk- 
bearing  transoms  are  not  the  transoms  first  lashed  to  the  frames 
in  making  them,  but  those  which  are  sent  out  after  the  frames 
are  in  position.  This  must  be  remembered  in  marking  the  posi- 
tions  of  the  transoms  on  the  legs  of  the  frames.  In  this  the  two 
frames  are  made  as  described  for  the  single-lock,  except  that  they 
are  of  the  same  width.  They  are  launched  as  described,  and 
pulled  forward  until  their  tops  are  about  ^  the  span  apart.  Two 
straining  beams  are  then  run  across,  the  road-bearing  transoms 
fastened  on  top  of  them  in  the  positions  previously  marked.  The 
frames  are  held  by  the  back  guys  until  all  is  ready,  when  they 
are  eased  off  and  the  bridge  locked.  The  roadway  is  then  laid  as 
usual. 

270. — Fai-  sjxn/s  greater  than  45  or  50 /^,  where  timber  of 
sufficient  size  is  obtainable,  the  Single  Sling  or  Treble  Sling 
may  be  used.  The  frames  are  made  as  has  been  described,  with 
the  following  additional  observations: 

In  the  Single  Sling  (Fig.  2),  in  marking  the  positions  of  the  dif- 
ferent spars,  the  three  locking  pieces  must  be  at  least  9  or  10  ft. 
above  the  roadway.  The  fork  piece  is  hauled  into  position  by 
snatch  blocks  lashed  to  the  top  of  each  leg  of  narrower  frame. 


PLATE   39. 


Double  Lock 

^^.^ -:s^^ 


PLATE  40. 


Spar  Bkidge^.  171 

after  which  the  blocks  are  used  to  get  the  center  transom  tempo- 
rarily into  position,  when  it  is  slung  by  the  ropes  that  are  to  hold 
it,  by  taking  several  turns  around  it  and  the  locking  pieces  with- 
out riding,  and  afterwards  twisted  up  to  the  proper  height  with  a 
pole. 

277. — In  the  Treble  Sling  (Pig.  3)  there  are  three  slung 
transoms,  one  from  the  forks  and  one  from  the  standards  on  each 
side  of  the  middle.  The  frames  are  constructed  as  already  de- 
scribed. (PI.  10,  Fig.  2,  being  one  in  plan.)  If  necessary,  the 
frames  may  be  strengthened  by  additional  braces  on  them  and 
further  braced  back  to  the  banks  by  ropes  attached  to  holdfasts 
and  otherwise  as  suggested  on  PI.  40,  Figs.  1  and  5,  vertical  braces 
being  shown  in  Fig.  3. 

278. — Other  expedients  for  crossing  small  gaps  are  the  use  of 
wagons  in  various  ways  for  supports,  brushwood  made  into 
gabions,  fascines,  etc.     (Figs.  6  and  7.) 

279.— A  liglit,  portable  truss  (Fig.  11)  can  be  made, 
where  boards  are  obtainable,  by  describing  two  arcs  of  circles 
with  radii  151  ft.,  on  opposite  sides  of  a  60  ft.  chord,  then  driving 
stakes  on  the  arcs  at  intervals  of  about  2  ft.,  against  which  5 
layers  on  top  and  6  layers  on  bottom  of  boards  1  in.  thick  x  12  in. 
wide,  breaking  joints,  are  bent  and  securely  nailed  together  every 
1  in.  with  tenpenny  nails.  The  lower  side  of  truss  is  made  one 
board  thicker  than  the  upper  and  is  completed  by  driving  G  in. 
spikes  through  every  6  in.  This  truss  will  be  about  6  ft.  deep, 
and,  allowing  2  ft.  at  each  end  for  resting  on  supports,  will  bridge 
a  span  56  ft. 

The  sides  are  connected  every  5  or  6  ft.  by  vertical  pieces  of 
I)lank  and  two  1-in.  iron  rods,  the  latter  on  the  sides  of  the  verti- 
cals, towards  the  middle.  If  iron  rods  are  not  obtainable,  rope  or 
wire  should  be  wrapped  aro\md  both  and  twisted  tightly.  The 
angles  at  the  ends  are  filled  with  wedge-shaped  pieces  and  the 
ends  securely  bolted,  hooped,  or  wrapped.  (Fig.  9.)  For  greater 
rigidity,  light  diagonal  braces  may  be  inserted  in  the  panels.  The 
top  can  be  made  straight  instead  of  curved  if  so  desired. 

These  trusses  are  used  in  pairs  and  are  applicable  to  a  variety 
of  structures  and  to  spaces  of  considerable  width.  Two  such 
trusses  with  a  central  support  of  trestles,  crib-work,  or  boats,  may 
be  used  for  116  ft.  (Fig.  11);  three  such  trusses  for  176  ft.,  etc. 
In  experiments  with  such  trusses  in  bridges,  1,800  lbs.  per  lineal 


172  Spar  Bridces. 

foot  has  been  applied  before  breaking;  and  by  covering  the  boards 
with  pitch  and  tar  before  nailing  together,  inserting  %  in.  bolts 
in  pairs  every  foot  of  length  on  lower  side,  and  nailing  boards 
against  the  edges,  3,500  lbs.  per  lineal  foot  was  applied  before 
breaking. 

280.  Siisi)tMisi<)ii  l>i'i(l<>'es.  For  spans  greater  than  60  ft., 
and  when  timbers  for  frames  cannot  be  procured,  some  form  of 
suspension  bridge  might  be  used.  Although  applicable  to  longer 
spans,  and  the  materials  more  easily  transported,  they  take  longer 
to  make  than  other  kinds. 

The  cables  may  be  of  iron  chains,  iron,  steel  or  fibrous  ropes, 
or  of  boards  nailed  together. 

281. — PI.  40a,  Pig.  1,  shows  one  with  the  roadway  hung  below 
the  cables,  with  a  camber  ^^y.  At  the  center,  the  roadway  should 
be  at  least  1  ft.  below  the  cables.  The  width  of  roadway  between 
side  rails  should  be  only  slightly  wider  than  wagon-wheel  tracks. 
(Pig.  2.)  On  the  banks,  the  cables  are  supported  by  timber  piers 
(Pig.  3),  having  a  broad  cap  (Pig.  4),  rounded  on  top,  over  which 
they  pass  at  a  distance  apart  of  9.5  ft.  The  cables  must  be 
securely  anchored  at  the  rear  to  heavy  logs  sunk  4  or  5  ft.  in  the 
ground,  or  otherwise,  and  drawn  in  until  the  sag  is  only  ^^y  or  ^\ 
of  the  span. 

282.  -In  Pig.  5,  part  of  the  roadway  is  hung  below  and  a  part 
rests  on  the  cables,  the  greatest  slope  of  road  being  1  on  6  for  100 
ft.  span  and  ^q  sag.    The  cables  are  only  7  ft.  apart. 

283. — In  Pig.  6,  the  roadway  is  built  on  trestles  supported  on 
the  cables.  Por  spans  130  ft.,  sag  ^^,  the  frames  form  the  sides  of 
equilateral  triangles  of  10  ft.  each.  To  construct  it,  the  curve  of 
the  cables  is  traced  on  the  ground,  the  trestle  legs  laid  on  it  and 
marked  where  they  cross  the  road  and  cable ;  those  for  each  half 
of  the  bridge  are  ranged  in  order  on  the  banks,  connected  to- 
gether as  placed  on  the  cables  and  hauled  out,  connected  at  the 
center,  the  curve  of  the  cables  adjusted  and  the  bridge  completed. 

284. — Pig.  7  is  a  suspension  bridge  of  which  the  cables  are 
made  of  boards  nailed  together  in  several  thicknesses  laid  hori- 
zontally, breaking  joints;  the  ends  are  spread  apart  and  wedge- 
shaped  blocks  inserted  and  anchored  by  several  rows  of  posts,  as 
shown  in  Pig.  8.  Each  cable,  as  made,  is  drawn  across  by  ropes^ 
anchored,  and  the   trestles  placed  from  both  ends  at  the  same 


Spar  Bridges.  173 

time.    Last  of  all,  spikes  loDg  enough  to  reach  entirely  through 
the  cable  are  driven  every  4  to  6  in. 

285. — Fig.  11  is  a  similar  bridge  supported  on  trestles  16  ft. 
long,  not  exceeding  20  ft.  high,  placed  at  intervals  of  40  ft.,  over 
which  suspends  the  two  board  cables,  14  ft.  apart.  On  these  are 
placed  low  trestles,  3  ft.  high,  dividing  the  spans  into  lengths  of  ' 
20  ft.  each ;  25  ft.  balks  are  used  and  the  roadway  laid  as  usual. 
The  cables  are  made  of  six  thicknesses,  of  1  in.  boards  12  in.  wide, 
breaking  joint,  nailed  and  spiked  every  4  to  6  in.,  and  bolted  by 
pairs  of  %  i^-  bolts  every  foot.  Three  thicknesses  of  boards  are 
first  nailed  together  and  drawn  across,  the  ends  anchored,  and 
then  the  other  three  boards  added. 

280. — For  light  foot  bridges  (Fig.  10),  across  narrow  gaps,  wire 
from  fences,  if  available,  could  be  used. for  the  cables  by  twisting 
a  number  together  and  passing  them  over  crotches  of  trees  and 
anchoring  to  stumps,  etc.,  in  rear,  and  then  laying  the  walk  simi- 
lar to  some  of  the  methods  previously  shown. 

287. — So  various  are  the  conditions  to  be  met  in  constructing 
bridges  that  seldom  will  any  one  type  meet  the  requirements,  but 
by  the  application  of  good  judgment  and  resource,  with  the  sug- 
gestions here  offered,  almost  any  gap  of  reasonable  width  may  be 
crossed,  if  not  by  one  type  or  another,  then  by  a  combination  of 
several  to  meet  the  emergency. 

The  varying  strength  of  timbers  makes  it  almost  impossible  to 
give  exact  dimensions  for  the  different  spars  to  be  used  in  the 
different  types,  but  a  general  idea  may  be  obtained  below  of.the 
amounts  and  average  dimensions  of  medium  strength  timber,  as 
yellow  pine.  For  weaker  timbers  some  of  the  sizes  will  have  to 
l)e  increased,  while  for  stronger  ones  there  will  be  an  excess  of 
strength  if  the  sizes  given  are  adhered  to,  but  the  desire  to  be  on 
the  side  of  safety  warrants  the  use  of  amounts  which  might,  by  a 
careful  mathematical  calculation,  appear  to  be  excessive. 

The  timbers  for  transoms,  ledgers,  braces,  balks,  flooring  and 
side  rails  should  be  selected  of  as  nearly  a  uniform  diameter 
throughout  as  possible  and  will  be  so  considered  in  giving  dimen- 
sions.   For  legs  or  standards  the  diameter  at  tip  will  be  given. 

For  a  9  ft.  roadway  with  15  ft.  spans,  5  balks  20  ft.  long  x  about 
G  in.  in  diam.  are  used,  and  placed  2)4  ft.  apart  from  center  to 
center.  For  the  flooring  are  used  poles  11  to  12  ft.  long  x  4  to  5 
in.  in  diam.     For  side  rails  2  poles  20  ft.  long,  4  to  6  in.  in  diam. 


174  Spar  Bridges. 

For  eacli  Six-legged  Trestle  (PL  36,  Fig.  1)  1  vertical  and 
2  bracing  legs  6  in.  diam.,  1  transom  12  ft.  x  8  in.,  2  foot  pieces  3  ft. 
X  8  in.,  10  oak  pins  2  in.  diam. 

For  eacli  Tie-block  Trestle  (Fig.  2)  2  legs  8  in.  diam.,  2 
transoms  15  ft.  x  8  in.,  4  tie  blocks  2  f t.  x  5  in.  x  6  in.,  2  braces  3  ft. 
X  2  in.  X  6  in.,  24  spikes,  1  rope,  1  rackstick. 

For  eaeli  Capped  Trestle  (Fig.  3)  4  legs  8  in.  diam.;  2 
braces  12  ft.  x  4  in.;  2  braces  15  ft  x  5  in.;  3  boards  12  ft.  x  2  in.  x 
12  in.;  4  ropes,  spikes. 

For  eacli  Two-legged  Trestle,  lashed,  (Fig.  4)  2  legs  4  ft. 
longer  than  height  of  trestle,  5  to  7  in.  tip ;  1  transom  15  ft.  x  9 
in.;  1  ledger  16  ft.  x  4  to  6  in.;  2  braces  3  to  5  in.  diam.;  6  ropes  30 
ft.  x  J  in.  diam.;  3  ropes  15  ft.  x  |  in.  diam. 

For  eacli  Tliree-legged  Trestle,  lashed,  (PI.  37,  Fig.  1)  6 
legs  3  to  5  in.  tip ;  4  transom  bearers  6  ft.  x  3  to  4  in.;  4  sticks  2 
ft.  x  2  to  3  in.;  6  ledgers  2  to  3  in.  diam.;  1  transom  15  ft.  x  9  in.; 
12  ropes  30  ft.  x  J  in.  diam.;  6  ropes  15  ft.  x  |  in.  diam. 

For  eacli  Four-legged  Trestle,  lashed,  (Fig.  2)  twice  the 
amount  given  for  each  two-legged  trestle,  plus  2  ledgers,  and  6 
lashings  15  ft.  loii^-. 

For  each  Single  T.ock  (PI.  38,  Fig.  4)  4  legs  22  to  25  ft.  x  7 
in.  tip  ;  1  ft.  transom  15  ft.  x  10  in.;  2  frame  transoms  15  ft.  x  6  in.; 

2  ledgfMs  15  ft,  X  4  to 6  in.;  4  braces  20  ft.  x  3  in.;  2  shore  sills  15 
ft.  xG  ill.  LdsJiinys,  4  transom  50  ft.  x  |  in.;  10  ledger  and 
brace  30  ft  x  J  in.;  10  balk  20  ft.  x  },  in.;  4  foot  50  ft.  x  1  in.;  8  guy 
150  ft.  x  1  in. 

For  each  Double  Lock  (PL  39,  Fig.  1)  4  legs  22  to  25  ft.  x 
7  in.  ti]) ;  2  straining  beams  25  ft.  x  8  in.;  2  road  transoms  15  ft.  x 
10  in.;  2  frame  transoms  15  ft.  x  6  in.;  2  ledgers  15  ft.  x  5  to  6  in.; 
4  braces  20  ft.  x  3  in.:  2  shore  sills  15  ft.  x  6  in.;  Lashings,  8  tran- 
som 50  ft.  x  I  in.;  14  ledger  and  brace  30  ft.  x  J  in.;  10  balk  20 
ft.  X  J  in.;  4  foot  50  ft.  x  1  in.;  8  guy  150  ft.  x  1  in.;  besides  axes  and 
other  tools,  and  anchorages,  holdfasts,  etc.,  on  banks. 

For  each  Single  Sling  (Fig.  2)  4  legs  35  to  45  ft.  x  6  in.  tip; 

3  top  and  fork  transoms  15  ft.  x  6  in.;  3  road  transoms  15  ft.  x  10 
in.;  2  ledgers  15  ft.  x  4  to  6  in.;  4  braces  20  ft  x  3  in.;  2  shore  sills 
15  ft.  x  6  in.;  10  balks  30  ft.  x  6  in.;  4  side  rails  30  ft.  x  4  to  6  in. 
Lashings  of  same  number,  size  and  length  as  for  Double  Lock. 
Stiffening  will  require  additional  spars  and  lashings,  depending 
upon  the  method  used. 


PLATE  40a. 


Fig.8.       Fig.  4 


Fig.6 


Fig.  10 


^.Af\. 


Spar  Bridges.  175 

For   eacli   Treble   Sling  (Fig.  3)  4  legs  50  ft.  x  6  in.  tip  ;  5 

road  transoms  15  ft.  x  10  in.;  3  top  and  fork  transoms  15  ft.  x  6 
in.;  2  lower  ledgers  15  ft.  x  4  to  6  in.;  4  lower  braces  20  ft.  x  3  in.; 
4  upper  braces  18  ft.  x  3  in.;  2  shore  sills  15  ft.  x  6  in.;  15  balks  5 
ft.  longer  than  ^  span  x  6  in.;  6  side  rails  5  ft.  longer  than  ^  span 
x  4  to  6  in.;  6  sling  racking  sticks  10  ft.  x  4  in.  Lashings,  4  foot  50 
ft.  X  1  in.;  8  guy  150  ft.  x  1  in.;  24  ledger  and  brace  30  ft.  x  |  in.; 
8  transom  50  ft.  x  |  in.;  40  or  50  balk  20  ft.  x  i  in.  Stiffening 
will  require  additional  spars  and  lashings,  depending  upon  the 
method  used. 

For  Suspension  Bridge  200  ft.  long  (PI.  40a,  Fig.  1)  4  to  8 
cables  180  ft.  x  1  in.;  16  cable  seizing  of  yarn  18  ft.  long  ;  12  lash- 
ings 50  ft.  X  I  in.;  10  lashings  30  ft.  x  i  in.;  100  lashings  20  ft.  x  | 
in.;  2  steel  wire  cables  400  ft.  x  1|  in.;  4  standards  26  ft.  x  10  in. 
tip ;  4  braces  22  ft.  x  3i  in.  tip ;  2  caps  12  ft.  x  10  in.;  2  sills  15  ft  • 
X  10  in.;  4  back  struts  36  ft.  x  4  in.  tip  ;  4  side  struts  32  ft.  x  3  in. 
tip ;  4  cable  props  30  ft.  x  5  in.  tip ;  4  horizontal  ties  30  ft.  x  3  in. 
tip ;  21  transoms  10  ft.  x  6  in.;  80  balks  13  ft.  x  6  in.;  40  side  rails 
20  ft.  X  6  in.;  for  anchorages  16  spars  5  ft.  x  7  in.  tip ;  2  spars  16  ft. 
X  20  in.;  2  spars  16  ft.  x  12  in.  f  round ;  10  spars  16  ft.  x  8  in.  f 
round ;  4  back  ties  50  ft.  x  |  in.  steel  rope  ;  4  ties  35  ft.  x  ^  in.  steel 
rope  ;  40  slings  total  600  ft.  x  J  in.  steel  rope  ;  4  guys.50  ft.  x  1  in.; 
4  rope  ladders. 

For  Suspension  Bridge  100  ft.  long  (Fig.  5)  4  to  8  cables, 
12  cable  seizings,  4  lashings,  12  lashings,  30  lashings  as  above  ;  2 
cables  180  ft.  x  3  in.  hemp  or  2  in.  steel ;  2  anchor  spars  18  ft.  x  15 
in.;  10  transoms  12  ft.  x  4  in.;  4  balks  25  ft.  x  6  in.;  10  side  rails  20 
ft.  X  4  in;  materials  for  piers  depending  on  circumstances. 

For  Suspension  Bridge  130  ft.  long  (Fig.  6)  4  to  8  cables; 
12  cable  seizings,  9  lashings,  104  lashings,  280  lashings  as  above ;  4 
cables  200  ft.x2|  in.  hemp  or  1|  in,  steel ;  2  anchor  spars  18  ft.x  18 
in.;  44  trestle  legs  13  ft.  x  3  in.  tip  ;  44  braces  15  ft.  x  2  in.  tip  ;  22 
transoms  9  f t.  x  4  in.;  80  ledgers  12  ft.  x  2  in.;  20  cable  ledgers  12 
ft.  X  5  in.;  2  shore  sills  10  ft.  x  5  in.;  48  balks  14  ft.  x  5  in.;  28  side 
rails  20  ft.  x  5  in.;  materials  for  piers  depending  on  circumstances. 

Besides  the  above  materials,  there  will  be  required  tools  for 
cutting  timber,  tackles  for  raising  frames,  shovels,  pickets,  etc., 
and,  where  not  mentioned,  the  ordinary  amounts  of  balks,  chess, 
side  rails,  etc. 


CHAPTi:n  X^  I.— Floatino    liiidoc 


288. — Tlie  i>assage  of  a  stream  may  be  effected,  in  many 
cases,  as  described  in  the  preceding  chapter.  If  the  methods 
there  hiid  down  are  not  suitable  or  expedient,  and  the  stream  can- 
not be  forded,  then  resort  must  be  had  to  ferry int?  by  boats,  rafts, 
flying  bridges,  or  to  floating  bridges. 

289. — Tlie  selection  of  a  place  and  means  of  crossing  a 
river  is  determined  by  a  reconnaissance,  which  should  be  as  de- 
tailed and  extensive  as  circumstances  will  permit,  and  oml)race 
the  following:— 

(a)  The  nature  of  the  banks. 

(b)  The  nature  of  the  bed. 

(c)  Position  and  dei^th  of  fords. 

(d)  Strength  of  the  current. 

(e)  Whether  tidal  or  otherwise. 

(f)  Probability  and  extent  of  floods. 

290. — Fords.  A  stream  with  a  moderate  current  may  be 
forded  by  infantry  when  its  depth  does  not  exceed  3  ft.,  and  by 
cavalry  and  carriages  when  its  depth  is  about  4.  ft.  The  requisites 
of  a  good  ford  are: — 

(a)  Banks  low,  but  not  marshy. 

(b)  Water  attaining  its  depth  gradually. 

(c)  Current  moderate. 

(d)  Stream  not  subject  to  freshets. 

(e)  Bottom  even,  hard,  and  tenacious. 

291 .-  In  a  mountainous  country,  the  bed  of  a  stream  is  likely  to 
be  covered  with  large  stones,  rendering  the  passage  of  carriages 
impracticable.  In  level  countries,  the  bed  of  the  stream  may  be 
composed  of  mud  or  quicksand,  rendering  passage  by  fording  im- 
possible. In  some  cases,  the  bottom  is  composed  of  fine  sand, 
which  is  hard  enouiih,  but  wliich.  by  the  action  of  the  hoofs  of  the 


'  UNIVERSITY 


PLATE  41. 


1^ ^ 


Floating  Bridges.  171) 

animals,  is  stirred  up;  the  current  then  carries  the  sand  away  and 
the'ford  is  deepened,  perhaps  so  much  as  to  become  unfordable. 
The  best  bottom  is  coarse  gravel. 

292.— Fords  are  usually  found  in  the  wider  and  more  -rapid 
parts  of  a  stream.  A  straight  reach  gives  the  most  uniform 
depth.  At  bends,  the  depth  will  generally  be  greater  at  the  con- 
cave bank  and  less  at  the  convex.     (PI.  41,  Figs.  1  and  3.) 

293. — To  determine  the  position  of  a  ford  : — 

(1)  A  number  of  mounted  men  may  be  sent  across  wherever 
there  is  a  probability  of  the  river  being  shallow  enough. 

(2)  Most  certain  method.  Float  down  the  stream  in  a  boat, 
keeping  in  the  swiftest  part  of  the  current,  where  the  water  is 
usually  deepest.  Hang  a  sounding  line  of  the  proper  length  over 
the  stern.     When  this  touches  bottom,  sound  across  the  stream. 

When  a  ford  is  discovered,  it  should  be  marked  by  stakes ; 
remarkable  objects  on  the  shore  should  be  noted ;  and  a  stake 
planted  at  the  water's  edge  and  marked,  in  order  that  any  rise  in 
the  water  may  be  at  once  evident. 

294. — A  stream,  otherwise  unfordable,  may  be  passed  : — 

(1)  By  crossing  it  in  a  slanting  direction.     (Fig.  2.) 

(2)  When  the  unfordable  portion  is  not  over  8  or  10  yards,  this 
may  be  filled  in  with  fascines  loaded  with  stones.     (Fig.  4.) 

(3)  When  the  bottom  is  muddy,  it  may  be  covered  with  bundles 
of  coarse  grass,  rushes,  or  twigs,  sunk  by  means  of  stones. 

(4)  A  portion  of  the  water  may  be  diverted  from  its  natural 
channel.     (Fig.  5.) 

295.^In  passing  a  stream  by  fording,  if  it  is  deep  and  the  cur- 
rent at  all  swift,  the  following  precautions  should  be  taken  : — 

(a)  Troops  passing  in  column  should  do  so  at  a  considerable 
interval,  in  order  to  avoid  choking  the  stream. 

(b)  If  boats  are  to  be  had,  a  few  should  be  stationed  below  the . 
ford,  to  assist  men  who  may  be  carried  down  by  the  current. 

(c)  If  boats  cannot  be  procured,  mounted  men  may  perform  the 
duties  described  in  the  foregoing  provision. 

(d)  In  place  of  provisions  "b*'  and  "c,"  a  life  line,  held  up  by 
casks,  may  be  stretched  across  the  stream. 

(e)  In  order  to  break  the  force  of  the  current,  cavalry  may  be 
stationed  in  the  stream,  above  the  point  of  crossing. 

296. — After  a  freshet,  a  ford  should  always  be  re-examined, 
lest  some  alteration  may  have  taken  place  in  the  bed  of  the 


1'^"  FU)ATIN(.      I>lv'll)(.i;s. 

Rtreani.  T1h>  i):iiiks  of  a  sli-caiu  tn  Ix'  foiMcd  slioukl,  if  necessary, 
be  scarped. 

The  velocity  of  a  stream  may  be  determined  by  throwing  in  a  light 
rod,  so* weighted  as  to  stand  vertically.  Note  the  distance  passed 
over  in  a  certain  number  of  seconds ;  then,  /g  the  mean  number 
of  feet  T)er  second  ^nves  the  velocity  in  miles  per  hour. 

2J)T.  Ice.  In  lii^h  latitudes,  during  the  winter,  rivers  are 
ireiiuently  covered  with  ice  of  sufficient  thickness  to  sustain  the 
heaviest  loads.  This  means  of  passing  a  stream  should  be  used 
with  great  circumspection.  A  change  of  temperature  may  not 
only  suddenly  destroy  the  natural  bridge,  but  render  the  river  im- 
passable by  any  method,  for  a  considerable  time,  in  consequence 
of  floating  ice. 

298.  Ice,  in  order  to  allow  of  passage,  should  be  of  the  follow- 
ing thickness: 

For  Infaiiliy.  sin^-lc   tile.  '2  yds.  distance,  on  a  line  of 

planks 2  in. 

For  Cavalry  or  light  guns,  w4th  interA^als 4  in. 

Heavy  tield-pieces 5  to  7  in. 

Heaviest  loads 10  in^ 

299. — When  there  is  any  doubt  as  to  the  strength  of  the  ice, 
two  tracks  of  plank  may  be  laid  for  the  carriage  wheels  to  run  on, 
or  the  wagon  may  be  transformed  into  a  kind  of  sled  by  fastening 
two  planks  under  the  wheels.     (Fig.  6.) 

The  thickness  of  ice  may  be  increased,  when  the  temperature  is 
low,  by  throwing  water  on  it.  When  a  stream  is  frozen  on  each 
side  but  open  in  the  middle,  in  consequence  of  the  velocity  of  the 
current,  a  boom  stretched  across  the  open  space  will  often  check 
the  velocity  sufficiently  to  allow  the  water  to  freeze. 

300. — If  a  stream  cannot  be  forded,  it  may  be  crossed  by  fer- 
rying or  by  constructing  a  bridge.  Ferrying  may  be  by  boat, 
raft,  or  flying  bridge;  rowed,  sheared,  or  hauled  across. 

301.-  Ferrying  by  Boat.  All  boats  available  should  be 
collected  and  taken  to  the  chosen  point  of  passage.  The  banks  of 
the  stream,  if  steep,  should  be  scarped  to  facilitate  embarkation. 
The  landing  should  be  farther  down  the  stream  than  the  point  of 
starting.  The  boats  should  be  arranged  along  the  shore  and 
numbered.  Entrance  to  the  boats  should  be  by  file,  the  soldiers 
taking  positions  on  opposite  sides  alternately.     Where  the  water 


l''i>()Ai'i\(i    l)i\'i  I)(;ks.  181 

is  shallow  near  the  shore,  the  boat  should  not  approach  the  bank 
so  closely  as  to  ground  as  the  men  tile  in.  The  unloading  should 
])e  made  in  the  same  manner  us  the  embarkation,  i.  e.,  by  file 
alternately  from  each  side  of  the  boat.  During  the  transit,  the 
men  should  remain  in  position  and  not  rise  up  suddenly  when  th^;-  -, 
boat  lurches.  ,   J^      ^^^   ^ 

In  i^assing  artillery,  the  piece  should  be  dismounted.    H^rse^lV^-, 
should,  ordinarily,  be  made  to  swim.     However,  if  the  boats^r^      ^  ""^ 
large  enough,  the  bottoms  may  be  covered  with  plank,  and  tn^^^v:^^Pf>^ 
horses  placed  crosswise,  facing  alternately  up  and  down  stream.  ^^ 

302. — Ferrying  by  Raft.  Rafts  may  be  made  of  logs,  lum- 
ber, casks,  and  other  material  suitable  for  the  purpose.  Their 
construction  is  the  same  as  explained  for  piers  of  bridges,  hence 
only  two  expedients  will  be  mentioned  here. 

303. — Tlie  Canvas  Ilaft.  No  other  material  being  avail- 
able, small  rafts  can  be  constructed  by  the  use  of  canvas  about  8 
X  12  ft.,  and  brushwood.  Wet  the  canvas  to  make  it  water-proof, 
and  lay  it  out  on  the  ground.  Across  the  width  place  sticks  in 
layers,  the  longest  near  the  middle.  The  sides  should  be 
strengthened  by  heavy  sticks  placed  lengthwise.  The  pile  of 
sticks  should  be  about  4  ft.  wide  in  the  center  and  sloping  off 
slightly  towards  the  ends,  3  ft.  high  and  8  ft.  long.  Over  this  pile 
a  second  piece  of  canvas,  after  being  wet,  should  be  placed.  The 
sides  of  the  canvas  on  the  ground  are  now  drawn  over  toward  each 
other  and  lashed  securely  with  a  lariat.  The  ends  are  folded 
neatly,  brought  up  towards  each  other,  and  lashed.  If  care  is 
taken  to  wet  the  canvas  thoroughly  and  make  it  water-tight,  this 
raft  will  carry  three  troopers  with  their  arms  and  accoutrements. 
By  lashing  several  together,  a  larger  number  of  men,  with  their 
arms  and  accoutrements,  can  be  carried. 

304. — Rafts  of  Skins.  Bags,  made  of  the  skins  of  animals, 
inflated  with  air  or  stuffed  with  hay  or  straw,  can  be  utilized  for 
crossing  streams,  and  have  been  used  from  ancient  times. 

305. — Rafts  are  more  suitable  for  the  embarkation  and  landing 
of  troops  of  all  arms  than  boats.  They  will  carry  a  larger  num- 
ber each  trip,  are  not  so  easily  injured  by  the  fire  of  the  enemy, 
and  draw  little  water.  On  the  other  hand,  they  cannot  be  navi- 
gated with  the  same  facility  as  boats,  move  much  more  slowly,  and 
hence  keep  the  troops  much  longer  under  fire;  cannot  be  directed 
with  certainty  on  a  fixed  point  when  the  stream  is  rapid,  and,  if 


182  i^YoATiNG  Bridges. 

the  passage  is  to  be  effected  secretly,  the  time  required  for  their 
construction  is  too  long  to  admit  of  their  use. 

306. — Tlie  Floating  Bridge.  This  may  be  formed  of  two 
boats  covered  with  a  platform,  constructed  as  follows: — (PI.  42, 
Fig.  1. — The  lashings  and  side  rails  are  omitted.)  From  5  to  7 
beams  of  the  same  thickness  are  laid  across  the  two  boats,  the  in- 
tervals between  the  beams  being  equal,  and  such  that  the  cover- 
ing planks  extend  1  ft.  beyond  the  extreme  beams.  The  interval 
between  the  boats  is  such  as  to  allow  the  beams  to  extend  2  ft. 
beyond  the  gunwales.  The  beams  are  lashed  to  the  boats,  the 
covering  planks  are  kept  in  place  by  2  side  rails,  laid  directly  over 
the  outer  beams,  and  lashed  down  to  them  ;  the  extreme  planks 
should  be  nailed  down. 

The  floating  bridge  can  be  navigated  by  oars  with  nearly  the 
same  facility  as  a  boat. 

307. — Tlie  Roi^e  Ferry.  The  rope  ferry,  which  is  used  in 
sluggish  streams,  consists  of  a  floating  support,  either  a  raft, 
floating  bridge,  or  a  large  boat.  It  is  drawn  by  hand  along  a  rope 
stretched  from  shore  to  shore. 

308. — Tlie  Trail  Bridge.  This  is  employed  in  streams  not 
more  than  150  yds.  in  width,  and  whose  current  is  not  less  than  3 
ft.  per  second,  or  2^  miles  per  hour.  The  rope  must  be  main- 
tained above  the  surface  of  the  water,  and,  consequently,  must  be 
drawn  very  tightly  by  means  of  a  windlass,  blocks,  and  falls,  or 
similar  expedients;  it  must,  also,  at  each  bank,  be  raised  some 
distance  above  the  water.     (PI.  42,  Fig.  3.) 

The  raft,  or  boat,  is  attached  to  a  pulley,  which  runs  on  a  sheer 
line,  and  by  means  of  a  rudder  is  given  such  a  position  that  its 
side  makes  an  angle  of  about  55°  with  the  direction  of  the 
current.  The  angle  of  55°  with  the  current  divides  its  force 
against  the  side  of  the  boat  into  two  components :  one,  per- 
pendicular to  the  sheer  line,  which  is  counteracted  by  the  resist- 
ance of  this  line ;  the  other,  parallel  to  it,  which  moves  the  boat. 
A  boat  for  this  kind  of  ferry  should  be  narrow  and  deep,  with 
nearly  vertical  sides. 

If  a  raft  is  used,  it  should'  be  lozenge-shaped,  the  acute  angle 
being  about  55°.    When  two  sides  are  parallel  to  tlie  current,  the 


PLATE  42. 


PLATE  43. 


Floating  Bridges.  187 

up-stream  side  will  then  be  in  the  most  favorable  position  for 
passage.     (PL  43,  Fig.  8.) 

309.— The  Flying  Bridge.  The  character  of  the  float  for 
this  ferry  is  the  same  as  in  the  preceding  case.  (PL  41,  Fig.  7 ; 
PL  42,  Fig.  2.)  This  bridge  is  resorted  to  when  the  stream  is  wider 
than  150  yds.  The  strain  on  the  sheer  line  being  very  great,  it  is 
replaced  by  a  cable  anchored  in  mid-stream,  in  which  case  the 
float  would  swing  between  two  landing  piers;  or  by  two  cables, 
one  anchored  on  either  bank,  the  float  swinging  between  four 
piers.  The  latter  requires  less  skill  in  manipulation.  The  angle 
which  the  float  makes  with  the  current  is  the  same  as  that  of  the 
•'trail"  bridge.  A  sharp  bend  may  be  utilized  for  anchoring  the 
cable,  as  shown  in  PL  42,  Fig.  4. 

The  length  of  a  swinging  cable  should  be  1%  to  2  times  the 
width  of  the  stream.  The  cable  should  be  supported  on  inter- 
mediate buoys  or  floats,  to  prevent  it  dragging  in  the  water. 

310. — Floating  Bridges  are  composed  of  a  roadway  and 
its  supports.  The  roadway  is  explained  in  the  preceding  chapter. 
The  supports  are  floating,  as  pontoons,  boats  of  commerce,  rafts 
of  barrels,  logs,  lumber,  inflated  skins  of  animals,  or  other  mate- 
rial. The  supports  are  called  floating  piers.  It  is  from  the 
character  of  the  support  that  the  bridge  derives  its  name. 

.311. — In  constructing  a  floating  bridge,  the  site  should  be 
tirst  selected  and  the  u'idth  of  the  stream  measured. 

In  selecting  a  site,  the  following  points  should  be  noted: — 

(a)  Proximity  to  a  road.  As  the  approaches  to  floating  bridges, 
having  frequently  to  be  constructed  across  meadows,  give  much 
trouble,  they  should  be  as  short  as  possible.  For  a  similar  reason, 
marshy  banks  are  undesirable. 

(b)  The  bed  of  the  stream,  if  anchors  are  required,  should  aftord 
good  holding  ground. 

(c)  A  bridge  can  be  best  defended  if  constructed  at  a  re-entering 
l)end  of  a  river. 

(d)  Use  can  frequently  be  made  of  islands  to  economize  mate- 
rial. 

312. — In  measuring  the  icidtli  of  the  stream,  if  it  cannot  be 
done  directly,  some  one  of  the  methods  explained  in  Chaj).  III. 
can  be  used. 

313. — It  should  be  remembered  that  a  wide  roadway  gives 
greater  steadiness  than  a  narrow  one.    In  making  calculations  for 


l88  Floating  Bridges. 

buoyancy,  the  weight  of  a  9  ft.  roadway  may  be  taken  at  80  lbs* 
per  running  foot. 

314. — Piers.  Of  whatever  material  the  floating  pier  is  made, 
the  following  points  should  be  observed: — 

(1)  The  available  buoyancy  of  each  pier  should  be  sufficient  to 
support  the  hea\  iest  load  that  can  be  brought  on  one  bay  of  the 
bridge. 

(2)  Piers  should  be  connected  with  each  other,  at  their  extremi- 
ties, by  tie  balks  or  lashings. 

(3)  To  insure  steadiness,  the  length  of  a  pier  should  be  at  least 
twice  the  width  of  the  roadway. 

(4)  The  water  way  between  piers  should,  if  possible,  be  more 
than  the  width  of  the  piers,  never  less. 

315. — Piers  of  open  boats.  In  forming  a  pier  of  open 
boats,  the  following  precautions  should  be  taken  : — 

(1)  The  boat  should  not  be  immersed  deeper  than  within  1  ft. 
of  the  gunwale. 

(2)  If  the  water  is  rough,  or  the  current  extremely  swift,  a  boat 
should  not  be  immersed  deeper  than  within  1  ft.  4  in.  of  the  gun- 
wale. 

(3)  Boats  should  be  placed  lu  bridge  with  bows  up  stream  or 
toward  the  current. 

(4)  If  the  stream  is  tidal,  the  bows  of  the  boats  should  be  alter- 
nately up  and  down  stream. 

(5)  Unless  the  boat  is  very  heavy  and  strong,  the  balks  should 
not  rest  on  the  gunwales;  a  central  transom  should  be  impro- 
vised by  resting  a  timber  on  the  thwarts  or  seats,  blocking  up 
from  underneath  and  bringing  the  weight  directly  on  the  keel- 
son.    (PI.  43,  Figs.  6  and  7.) 

(6)  Large  boats  should  be  placed  where  the  current  is  swiftest, 
also  as  the  first  and  last  boats  in  bridge. 

316. — Tlie  buoyancy  of  a  boat  may  be  found  by  one  of 
the  following  rules  :^ 

(1)  To  find  the  available  buoyancy  load  the  boat  with  unarmed 
men  to  a  safe  depth.  Multiply  the  number  of  men  thus  loaded 
by  160.    The  result  will  be  the  available  buoyancy  in  pounds, 

(2)  If  the  boat  is  afloat  and  empty,  the  available  buoyancy  may 
be  found  by  calculating  the  volume  between  the  then  water  line 
and  the  "  safe  load  •'  line,  and  multiplying  by  62J. 


Floating  Bridges. 


181) 


(3)  To  find  the  total  buoyancy.  If  the  boat  is  of  nearly  uni- 
form section,  the  area  of  the  section  multiplied  by  the  length  of 
the  boat  will  give  the  cubic  contents.  A  cubic  foot  of  water 
weighs  62^  pounds. 

Hence,  if  the  dimensions  of  a  boat  are  taken  in  feet,  the  con- 
tents will  be  cubic  feet,  and  this,  multiplied  by  62|,  will  give  the 
displacement  of  the  boat ;  from  this  subtract  the  weight  of  the 
boat ;  this  will  give  the  total  buoyancy. 

*}1  7.— To  find  tlie  leiigtli  of  a  bay. — First  find  the  avail 
able  buoyancy  of  the  boat.  Then  find  the  weight  per  running 
foot  of  the  load  the  bridge  is  to  bear,  and  to  this,  add  the  weight 
per  running  foot  of  the  roadway.  Divide  the  available  buoyancy 
by  this  sum.  The  quotient  will  be  the  distance  from  center  to 
center  that  boats  should  be  placed  apart.  Thus: — Suppose  the 
weight  per  running  foot  is  480  lbs.,  that  the  roadway  is  80  lbs. 
per  running  foot.  .'.  480+80r=:560.  The  available  buoyancy  is 
found  by  one  of  the  preceding  ruleS;  to  be  5,600  lbs.  .*.  5,600-j- 
560=10.  ^  ^ 

318.— The  open  boats  may  be: — (1)  Those  of  commerce  usually 
found  on  streams.  (2)  Regularly  constructed  pontons.  (3)  Im- 
provised boats. 

The  first  class  requires  no  description.  The  second  class  com- 
prises the  canvas  ponton  used  in  the  Advance  Guard  Train,  and  the 
boat  or  barge  used  in  the  Reserve  Train,  of  the  U.  S. 

319. — The  table  below  gives  the  dimensions  of  the  ponton  in 
the  U.  S.  Advance  Guard  Train,  shown  in  PI.  47. 

Canvas  Ponton  21'  x  5'  4"x2'  4".    Weight,  510  lbs. 

Balks  22'x4i"x4i". 

Side  Rails  same  as  Balks. 

Chess  ll'xl2"xli". 


WEIGHTS  FOR  ADVANCE  GUARD  TRAIN. 


Ponton 
Chess . 
Trestle 
Tool . . . 
Forii'e. 


Wagon. 

Load. 

Total. 

lbs. 

lbs. 

lbs. 

1,750 

1,985 

3,735 

1,750 

1,856 

3,606 

1,750 

2,060 

3,810 

1,700 

1,938 

3,638 

1,217 

1,166 

3,383 

190 


Floating  Bridges. 


320.--Th3  table  below  gives  the  dimensions  of  the  Ponton  in 
the  U.  S.  Reserve  Train,  shown  in  PI.  48. 
Ponton  31'x5'  8"x2'  7".     Weight  1,600  lbs. 
Balks  27'x5"x5"  for  a  20'  span. 
Trestle  Balks  21'8"x.V'xr)". 
Chess  13'xl2"xli". 
Side  Rails  same  as  Balks. 

WEIGHTS  FOR  RESERVE  TRAIN. 


Wagon. 

Load. 

TotaL 

Ponton 

lbs. 
2,200 
1,750 
2,200 
1,700 
2,217 

lbs. 

2,900 

2,280 

2,6;^ 

2,100 
1,166 

lbs. 

5,100 

4,030 
4,835 
3,800 
3,383 

Chess 

Trestle 

Tool 

Forge 

321. — Iniprovisecl  Boats.  To  reduce  the  amount  of  trans- 
portation required  by  an  army  is  a  very  important  consideration, 
hence  the  value  of  the  following  expedients. 

322.-Tlie  Crib  Ponton.  This  boat  is  18  ft.  long,  5  ft. 
wide,  2 J  ft.  deep  and  covered  with  canvas.  Construction.  (1) 
Let  stakes  4  ft.  long,  2J  in.  in  diameter,  and  2  ft.  apart,  be  driven 
into  the  ground,  (PI.  44,  Figs.  1,  2  and  3),  to  the  dejithof  about  1 
ft.,  so  as  to  enclose  a  space  of  the  proper  size  for  the  top  of  the 
boat.  The  tops  of  the  stakes  should  be  in  the  same  horizontal 
plane.  This  may  be  tested  by  placing  a  straight  edge  on  them. 
Those  that  are  too  high  can  then  be  driven  down. 

(2)  Nail  boards  against  the  outside  of  the  stakes,  extending 
4  in.  over  their  tops. 

(3)  Cross-pieces,  of  the  same  diameter  as  the  stakes,  are  laid 
across  the  tops  and  pinned  down  upon  them  w4th  wooden  pins. 

(4)  Nail  the  side  boards  to  the  ends  of  the  cross-pieces,  and 
cover  the  bottom  of  the  boat,  which  in  its  inverted  position  is  now 
on  top,  with  boards,  and  nail  the  projecting  edges  of  the  side- 
boards to  the  bottom  securely. 

(5)  Finish  boarding  sides  and  ends  to  the  proper  depth. 

(6)  The  frame  is  now  ready  to  be  covered  with  canvas.  For  a 
boat  of  the  foregoing  dimensions,  the  canvas  should  be  23|  ft.  x 


PLATE  44. 


Fig.  1. 


Fig.  2 


JW^I^^^SH^fc^^^H^^ 


Fig.  4 


Fig.  6. 


Fig.? 


Fig  5 


aaaammasa^  .iiiiL iliiiIhiiii ,i, iimj.iiM jli ,i ukimi WWM 


Ploatinc}  Bridges.  103 

10^  ft.,  about  6  in.  being  allowed  for  lap.  The  canvas  may  be  put 
together  in  any  number  of  pieces  by  daubing  the  edges  of  the 
seams  with  a  waterproof  composition  and  connecting  them  with 
ordinary  carpet  tacks. 

(7)  The  canvas  having  been  prepared,  it  should  now  be  coatt'cl 
with  a  waterproof  composition.  Tallow,  put  on  hot,  will  do  if 
nothing  better  can  be  found. 

(8)  Place  the  canvas  on  the  frame,  coated  side  downward.  Tack 
the  canvas  to  the  frame  and  cover  w4th  waterproof  composition. 

(9)  Spike  or  pin  2  or  3  stout  poles  to  the  bottom  longitudinally 
(not  shown  in  drawing)  to  keep  the  bottom  from  abraiding.  If 
these  poles  are  allowed  to  project  about  6  in.  at  each  end,  they 
will  assist  in  launching. 

(10)  Loosen  the  stakes  from  the  ground  by  means  of  levers. 
Turn  the  boat  over  and  saw  off  the  stakes  about  2  in.  below  the 
top  edge  of  the  side  and  end  boards. 

(11)  Pin  stout  poles  to  the  top  of  the  stakes  on  the  sides  and 
ends,  and  nail  the  side  and  end  boards  securely  to  them. 

(12)  The  side  poles  should  x^roject  about  6  in.  beyond  the  ends 
corresponding  to  those  on  the  bottom,  and  be  lashed  to  the  bottom 
poles  by  means  of  a  rope  loop  and  rack  stick.  (Not  shown  in 
drawing.) 

(13)  Turn  the  canvas  over  the  top  poles  and  tack  it  dow^n.  The 
boat  is  finished. 

323. — Tlie  Box  Ponton.  In  localities  where  planks  and 
boards  can  be  conveniently  procured,  pontons  may  be  constructed 
very  expeditiously  by  placing  two  partitions  of  2  in.  plank,  each  5 
ft.  long  and  2^2  ft.  high,  in  parallel  positions,  on  the  top  and  ends 
of  which  boards  are  nailed.  (PI.  44,  Fig.  4.)  The  box  thus  formed 
to  be  covered  with  pitched  canvas,  as  described  in  the  mode  of 
constructing  crib  pontons.  Where  sound  lumber  is  at  hand,  the 
box  ponton  will  be  more  easily  and  expeditiously  constructed 
than  the  crib  ponton,  but  if  plank  is  not  at  hand  it  may  be  prefer- 
able to  use  poles  or  split  timber  rather  than  wait  for  it. 

324.— Wagon  Body  Ponton.  Ordinary  wagon  bodies, 
covered  with  waterproof  canvas  or  india  rubber  blankets,  may  be 
used  either  as  boats  or  pontons.  The  small  capacity  of  the  wagon 
body  requires  such  pontons  to  be  placed  more  closely,  to  compen- 
sate for  it. 

325. — Piors  of  Casks.      In  order  to  determine  the  number 


lOit  Floatinc;    l)i:ii)(iKs. 

of  casks  necessary  to  form  a  pier,  the  buoyancy  of  a  cask  must  be 
calculated.    This  may  be  done  by  one  of  the  following  rules  : — 

(1)  Find  the  contents  of  the  cask  in  gallons  and  multiply  this 
by  S}^^ ;  the  result  will  be  almost  the  total  buoyancy  in  pounds. 

(2)  By  the  formula 

5c2  1  — W       X 

in  which  c  is  the  circumference  of  the  cask  in  feet  half  way  be- 
tween the  bung  and  the  extreme  end;  1  is  the  length  in  feet,  ex-, 
elusive  of  projections,  measured  along  a  stave,  and  W   is  the 
weight  of  the  cask  in  pounds ;  x  being  the  total  buoyancy. 

If  the  cask  is  closed,  j^^  of  the  total  buoyancy  equals  the  avail- 
able buoyancy. 

326. — To  find  the  distance  between  two  piers  of  casks  :  Find 
the  available  buoyancy  of  each  cask.  Multiply  this  by  the  num- 
ber of  casks  in  the  pier.  This  gives  the  available  buoyancy  of  the 
pier.  To  the  weight  per  running  foot  that  the  bridge  is  to  bear 
add  the  weight  per  running  foot  of  the  superstructure.  Divide 
the  available  buoyancy  of  the  jjier  by  this  sum;  the  quotient  will 
be  the  required  distance. 

327. — In  regard  to  p?>rs  of  casks,  the  following  should  be 
noted : 

(1)  That  piers  of  casks,  when  in  bridge,  should  always  be  rigidly 
connected  to  each  other  at  their  ends  by  tie  balks. 

(2)  That  the  tie  balks  should  be  lashed  to  both  gunnels  of  each 
pier. 

(3)  That  while  the  roadway  balks  may  not  be  lashed  to  the 
gunnels  and  to  each  other,  it  should  be  done  if  there  is  much 
sway  on  the  bridge. 

828. — Piers  of  Open  Casks.  This  is  the  simplest  and 
most  convenient  method  of  using  casks  for  piers,  as  it  requires 
only  a  few  nails  and  poles,  dispensing  with  rojjes  which  are 
sometimes  hard  to  procure. 

To  make  a  raft  of  this  kind,  as  shown  in  P].  44,  Figs.  5  and  6, 
stand  10  or  12  barrels  side  by  side,  touching  each  other ;  nail  4 
poles  across  the  outside  of  the  barrels,  two  at  top,  two  at  bottom, 
the  nails  being  driven  from  the  inside  into  the  poles,  which,  as 
the  heads  are  out,  can  easily  be  done.  Place  another  row  of  bar- 
rels beside  the  row  thus  fastened  together  and  nail  them  to  the 
two  poles  of  this  row.    Nail  two  poles  to  the  outside  of  the  second 


Floating  Bridges.  195 

row  of  barrels,  one  at  top  and  one  at  bottom ;  push  the  barrels 
thus  connected  iiito  the  water. 

If  too  many  rows  are  connected  on  land  they  will  become  too 
heavy  to  handle.  Any  number  of  rows,  however,  can  be  attached 
in  the  manner  described  above.  When  the  raft  is  completed,  the 
projecting  ends  of  the  poles  outside  are  lashed  together,  and,  at 
the  points  of  contact  of  the  barrels,  a  stout  wire  nail  should  be 
driven  through  and  clinched. 

329. — The  total  buoyancy  of  a  cask  may  be  calculated  by  the 
formula  given  above.  If  this  should  be  400  lbs.,  the  safe  load  for 
smooth  water  would  be  at  least  300  lbs.;  that  is,  the  available 
buoyancy  is  about  J  the  total  buoyancy.  A  square  raft  of  10  such 
barrels  to  a  side  would  carry  safely  30,000  lbs. 

330.--Piers  of  closed  casks.  The  usual  method  of  form- 
ing large  casks  into  a  pier  is  shown  in  PI.  43,  Figs.  1  and  2.  The 
following  are  the  successive  steps  in  its  construction  :— 

Stores  required  for  a  pier  of  7  casks  :  7  casks  ;  2  gunnels  ;  2 
slings;   12  braces. 

To  build  a  pier  of  the  foregoing  stores,  1  N.  C.  O.  and  16  men 
will  be  required.  The  detachment  is  marched  to  the  site  on 
which  the  material  is  placed  and  forms  the  casks  into  piers  by  the 
following  commands  and  means,  4  men  being  detailed  as  gunnel- 
men  and  12  as  bracemen. 

(1)  Alig;ii  casks.  At  this  command,  the  casks  are  brought 
to  the  designated  place  by  the  bracemen  and  aligned,  touching 
each  other,  bung  uppermost. 

(2)  Place  giiiiiiels.  At  this  command,  the  gunnels  are 
placed  on  the  outer  ends  of  the  casks  by  the  gunnelmen. 

(3)  Adjust  slings.  At  this  command,  gunnelmen  bring  up 
the  slings  and  stand  at  the  ends  of  the  gunnels,  the  bracemen  be- 
ing opposite  the  intervals  between  the  casks.  The  gunnelmen  at 
one  end  place  the  eyes  of  the  slings  over  the  ends  of  the  gunnels, 
and  those  at  the  other  end  secure  the  slings  to  the  ends  of  the 
gunnels  by  a  round  turn  and  two  half -hitches.  The  bracemen 
keep  the  slings  under  the  ends  of  the  casks  with  their  feet.  A 
sling  is  made  of  1  in.  rope  and  of  sufficient  length  for  an  eye 
splice  1  ft.  long,  at  one  end. 

(4)  Fasten  braces.  At  this  command,  the  bracemen,  hav- 
ing provided  themselves  with  braces,  pass  the  eye  of  the  brace 
under  the  sling  in  the  center  of  their  interval,  the  end  passed 


1 '.♦<■»  Floatinc;  Bkidges. 

through  thi^  eye  and  the  brace  hauled  taut,  the  sling  being 
steadied  by  either  loot.  The  brace  is  then  brought  up  outside 
the  gunnel,  directly  over  the  eye  and  a  turn  round  the  gunnel 
taken  to  the  left  of  the  standing  part. 

(5)  Haul  taut.  At  this  command,  each  braceman  removes 
his  foot  from  the  sling  and  hauls  up  the  standing  part  of  his 
brace  with  his  right  hand,  holding  on  to  the  turn  with  his  left ; 
as  soon  as  the  brace  is  taut,  the  turn  is  held  with  the  left  hand 
and  the  remainder  of  the  brace  in  a  coil  is  placed  on  the  cask  to 
the  left. 

(G)  Cross  hi'aces.  At  this  command,  each  braceman  takes 
the  brace  of  the  man  opposite  him  from  the  cask  on  his  right, 
passing  it  between  the  standing  part  of  his  brace  and  the  cask  on 
his  left,  then  back  between  his  brace  and  the  cask  on  his  right, 
keeping  the  turn  below  the  figure  of  eight  knot  on  his  own  brace. 
The  end  is  then  placed  on  the  cask  on  his  right.  Each  man  then 
takes  back  his  own  brace  from  the  cask  on  his  left,  passes  it  under 
the  gunnel  to  the  left  of  the  standing  part,  places  one  foot  against 
the  gunnel  and  hauls  taut. 

(7)  llock  and  liaiil  taut.  The  bracemen,  assisted  by  the 
gunnelmen,  at  this  command,  rock  the  pier  backwards  and  for- 
wards, the  bracomen  taking  in  the  slack  of  their  braces.  . 

(8)  Steady.     At  this  conimand,  the  bracemen  cease  h^miag.    — ^ 
ta»4  and  take  a  turn  round  the  gunnel  to  the  left  of  the  previous 
turns. 

(9)  Seevire  l)races.  At  this  command,  the  braces  are  made 
fast  by  two  half -hitches  round  the  two  parts  of  their  own  braces, 
close  to  the  gunnels,  drawing  the  two  parts  close  together  and 
placing  the  spare  ends  of  the  braces  between  the  casks. 

(10)  Turn  tlie  i)ier  to  tlie  right  and  adjust  sling;.  At 
this  command,  the  bracemen  on  the  left  side,  assisted  by  the  gun- 
nelmen, turn  the  pier  on  its  right  side.  The  bracemen  on  the 
left  side  adjust  the  left  sling. 

(11)  TjOAVor  tlic  ])ier,  turn  to  tlie  left,  and  adjust 
sling.  At  this  command,  the  bracemen  on  the  left,  assisted  by 
the  gunnelmen,  lower  the  pier.  The  bracemen  on  the  right, 
assisted  by  the  gunnelmen,  then  turn  the  pier  to  the  left.  The 
bracemen  on  the  right  then  adjust  the  right  sling.  The  pier  is 
complete. 


Floatinc;  Bkii)(;es.  11)7 

8^31.  -Should  the  casks  be  very  small,  they  may  be  put  to- 
gether as  above  described,  forming  small  piers.  These  can  then 
be  united  in  one  large  pier  by  cross  gunnels. 

332. — Another  method  of  forming  casks  into  a  pier  is  as  fol- 
lows :— (Figs.  3  and  4.) 

Fasten  the  braces  to  a  balk,  two  braces  for  each  cask.  Stretch 
out  the  braces  perpendicular  to  the  balk  and  lay  the  casks  bung 
uppermost,  end  to  end,  on  each  side  of  the  balk,  each  cask  over 
its  own  braces.  Upon  the  cask  lay  two  gunnels,  fastened  together 
at  the  ends  and  one  or  two  intermediate  points  by  lashings,  the 
distance  between  the  gunnels  being  less  than  a  bung  diameter  of 
a  cask.  Secure  the  braces  to  the  gunnels  by  two  round  turns  and 
two  half-hitches.  The  lashings  connecting  the  gunnels  are  then 
racked  up.  The  two  end  gunnel  lashings  are  lashed  to  the  balk 
beneath  the  casks  and  these  lashings  are  racked  up  taut.  The 
pier  is  then  complete. 

333. — The  barrels  may  be  held  in  ^  frame,  as  shown  in  PI.  44, 
Figs.  7  and  8. 

334. — Piers  of  XiOgs.  In  order  to  determine  the  number 
of  logs  necessary  to  form  a  pier,  the  buoyancy  of  a  log  must  be 
calculated. 

To  find  the  total  buoyancy  of  a  log.  Multiply  the  solid  contents 
of  a  log  by  the  difference  between  the  weight  of  a  cubic  foot  of 
the  log  and  a  cubic  foot  of  water. 

335. — To  find  the  solid  contents  of  a  log. 

(1)  Take  a  mean  of  the  girths  or  circumference  at  the  ends  in 
feet  and  decimals.  Square  this  mean  and  multiply  it  by  the  dec- 
imal .079^^6.  Multiply  this  product  by  the  length  of  the  log  in 
feet. 

(2)  Multiply  the  square  of  1  of  the  mean  girth  by  twice  the 
length  of  the  trunk. 

330.-  The  weight  per  cubic  foot  of  the  timbers  usually  met 
with  will  be  found  in  Chap.  XV. 

337. — Required  the  total  buoyancy  of  a  pine  log  whose  mean 
girth  is  6  ft.  and  whose  length  is  35  ft. 
Applying  rule  2,  we  have 

fx«x35x2  =  100*  cu.  ft. 
100,^  X  (62 i  -  40)  =  100|  X  221  =  100.8  x  22.5  =  2,268  lbs. 
As  lumber  absorbs  water,  the  availahle  buoyancy  is  taken  as  % 
the  total  buoyancy. 


198  Floating  Bridges. 

338.— To  form  a  pier  of  logs.  (PI.  43,  Fig.  5.)  The  larg 
est  and  longest  logs  should  be  selected.  Branches  and  knots 
should  be  trimmed  off.  The  ends  of  the  logs  should  be  painted  if 
the  raft  is  to  be  used  any  length  of  time.  The  raft  should  be 
built  in  the  water.  Select  a  place  where  there  is  little  current 
and  where  the  bank  slopes  gently  to  the  stream.  Throw  the  tim- 
ber into  the  water  and  moor  it  close  to  the  shore.  Note  the  nat- 
ural position  of  each  log  in  the  water  before  putting  it  in  the  raft. 
The  upstream  end  of  each  log  should  be  drawn  on  shore  and  bev- 
eled to  a  whistle  shape,  so  as  to  present  less  obstruction  to  the 
action  of  the  current. 

Arrange  the  timber  in  the  position  it  is  to  have  in  the  raft  the 
butts  alternately  up  and  down  stream,  the  up-stream  ends  forming 
a  right  angle,  salient  up-stream.  The  first  log  is  brought  along- 
side the  shore  and  the  end  of  a  plank  or  a  small  trunk  of  a  tree 
fastened  with  trenails  or  spikes  to  it  about  3  ft.  from  each  end. 
The  log  is  then  pushed  off  a  little,  a  second  log  brought  up  under 
the  transoms  and  in  close  contact  with  the  first.  The  second  log 
is  then  spiked  like  the  first,  and  so  on  for  each  remaining  log. 
Care  must  be  taken  to  place  the  whistle  ends  up  stream  with  the 
bevel  underneath,  and  to  spike  the  transoms  perpendicular  to  the 
logs.  If  the  stream  is  very  gentle,  the  up-stream  ends  of  the  logs 
may  be  parallel  to  the  transom. 

Another  method  is  to  lash  the  logs  together  and  fasten  on  the 
transoms  with  spikes  or  trenails.  Or,  lash  the  logs  together  and 
lash  the  transoms  to  the  logs,  tightening  the  lashings  with  rack 
sticks. 

339. — Two  additional  transoms  should  be  placed  on  the  raft 
by  whatever  method  employed  in  putting  on  the  first.  They 
should  be  the  distance  of  the  roadway  or  platform  apart,  at  equal 
distances  from  the  center  of  gravity  of  the  raft,  and  bear  upon  all 
the  logs.  In  order  to  obtain  sufficient  buoyancy,  and  allow  suf- 
ficient water  way,  several  courses  of  timber  may  have  to  be  era- 
ployed.  For  use  in  a  bridge,  a  raft  should  have  an  available 
buoyancy  of  15,000  lbs. 

340. — If  the  raft  is  to  be  used  as  a  flying  bridge,  it  should 
have  the  shape  of  a  lozenge.     (PI.  43.  Fig.  8.) 

3  41.  —  Ancliors.  Anchors  for  the  U.  S.  Advance  Guard 
Bridge  Train   weigh  75  lbs.,  and  for  the  reserve   train  150  lbs. 


r^  Of    THE  ^ 

1BSIVEBBITY 


PLATE  45. 


PLATE  46. 


Fig  1 


Fig.2, 


PLATE    47. 


PLATE    48 


Floating  Bridges.  207 

These  will  be  sufficient  for  moderate  streams.  An  anchor  with 
the  names  of  the  various  parts  is  shown  in  PI.  45,  Fig.  1. 

342.— The  distance  of  the  anchor  from  the  bridge  should  be 
at  least  10  times  the  depth  of  the  stream,  otherwise  the  bow  of 
the  boat  or  ponton  will  sink  too  deep  in  the  water.  The  direction 
of  the  cable  must  be  the  same  as  the  current.  The  anchor  cable 
should  be  of  1  in.  rope  and  attached  to  the  anchor  ring  by  a  fisher- 
man's bend.  A  buoy  might  be  attached  to  the  anchor  by  means 
of  a  3^^-in.  breast  line,  in  order  to  mark  its  position  and  serve  as  a 
means  of  raising  it.  The  breast  line  is  attached  to  the  buoy  ring 
by  a  fisherman's  bend  and  round  the  shank  of  the  anchor,  close 
to  the  crown,  by  a  clove  hitch. 

343. — The  number  of  anchors  will  depend  on  the  strength  of 
the  current.  It  is  generally  sufficient  to  cast  an  anchor  up-stream 
for  every  alternate  boat  or  ponton,  and  half  that  number  down- 
stream. If  the  stream  is  rapid,  every  boat  should  be  anchored 
up-stream. 

If  very  rajnd,  the  bridge  must  be  secured  to  a  hawser,  as  shown 
in  PL  46,  Fig.  1.  If  the  bridge  is  short,  ropes  can  be  stretched  from 
the  piers  to  the  banks.  (Fig.  2.)  If  anchors  are  scarce,  one  may 
be  attached  to  two  piers.    (Fig.  3.) 

Before  being  cast,  the  anchor  should  be  well  stocked.  Rafts  of 
casks  or  timbers  bring  a  greater  strain  on  anchors  than  boats  or 
pontons. 

344. — Substitutes  for  Aiicliors.  One  or  two  spare  wheels 
with  tires  and  felloes  removed.  (PI.  45,  Figs.  3  and  4.)  Two  or 
more  pick-axes,  laid  together  or  fixed  on  one  handle.  (PI.  46,  Fig. 
4.)  A  harrow  with  lengthened  teeth,  loaded  with  stones.  Gabions 
filled  with  stones.  Large  stones  or  railway  irons.  Nets  filled  with 
stones.    Frame  filled  with  stones.    (PL  45,  Fig.  2.) 

Care  must  be  taken  to  allow  the  anchor  to  fall  in  good  holding 
ground.  For  this  purpose,  a  direction  oblique  to  the  current  may 
sometimes  be  allowed. 

345.— Forming  Floating  Bridges.  Floating  bridges  may 
be  formed  in  the  following  ways  :— 

(1)  By  successive  pontons  or  boats. 

(2)  By  parts. 

(3)  By  rafts.  ,  ,,,  ,„,     ''^> 

(4)  Byconversion.  UNIVERSITY 


208  Floating  Bridges. 

340.— By  Successive  Pontons.  (PI.  49.)  This  may  be 
done  in  two  ways  : — 

(1)  By  adding  to  the  head  of  the  bridge,  the  tail  being  station- 
ary. This  method  requires  the  roadway  material  to  be  carried  an 
increasing  distance.  The  men,  however,  do  not  have  to  work  in 
the  water. 

(2)  By  adding  to  the  tail  of  the  bridge,  the  head,  already  con- 
structed, being  constantly  pushed  into  the  stream.  The  materials 
do  not  have  to  be  carried  so  far  as  in  the  first  case  but  it  requires 
a  number  of  men  to  work  in  the  water  and  is  not  advantageous 
where  the  bank  is  steep. 

In  the  first  method,  those  boats  or  pontons  which  cast  up 
stream  anchors  should  be  moored  above  the  approach  to  the 
bridge,  the  others  below. 

347. — By  Parts.  (PI.  49.)  In  this  method,  the  boats  or 
pontons  are  brought  close  to  the  shore  above  the  bridge.  For 
convenience  in  putting  the  parts  together  several  chess  are  laid 
from,  the  bank  to  the  interior  gunwale  of  one  boat  or  ponton.  The 
boats  or  pontons  forming  the  part  are  then  brought  in  place  and 
balks  placed  on  them.  The  chess  forming  the  roadway  are  then 
placed  on  the  balks,  excepting  a  sufficient  number  at  each  end  of 
the  i)art  to  allow  for  the  insertion  of  a  bay  between  the  parts. 
The  parts,  all  constructed  as  directed,  are  then  placed  in  position, 
each  part  carrying  enough  material  to  construct  the  connecting 
bay.  The  parts  are  joined  with  each  other  and  with  the  abut- 
ment bay,  which  has  been  previously  constructed. 

348.— By  Rafts.  Each  raft  formed  of  2  or  more  piers,  is 
constructed  complete  and  the  rafts  come  into  bridge  in  succes- 
sion. Each  of  the  methods,  bridge  by  raft  and  bridge  by  parts, 
has  the  advantage  of  simultaneously  employing  a  large  number 
of  men.    (PI.  49.) 

349.  —By  Conversion.  (PI.  49.)  In  this  method,  the  bridge 
is  put  together  entire  along  the  shore  above  the  selected  site.  A 
tributary  stream  may  be  advantageous  for  this  purpose.  The 
bridge  is  then  floated  toward  the  site,  care  being  taken  to  prevent 
the  i>ivot  end  from  touching  the  shore  and  the  wheeling  end  from 
turning  too  fast. 

350. — The  various  methods  above  described  may  be  combined 
in  the  construction  of  one  bridge. 


PLATE    49. 


I 


Floating  Bridges.  211 

The  connection  of  the  bridge  with  the  shore  may  be  made  by 
allowing  the  balks  to  rest  on  an  abutment  sill  let  about  one  foot 
into  the  ground,  or  by  a  trestle. 

351.— If  the  stream  is  to  remain  open  to  traffic,  it  is  well  to 
have  two  or  more  rafts  in  mid-stream,  arranged  to  swing  so  as  to 
allow  boats  to  pass,  or  the  halves  of  the  bridge  may  be  swung  for 
this  purpose.  Usually  the  passage  is  made  by  allowing  the  rafts 
or  halves  to  swing  with  the  current ;  they  are  then  brought  back 
against  the  current. 

352. — Floating  objects.  Some  arrangement  should  be 
made  to  protect  the  bridge  from  floating  objects.  This  may  be 
done  : — 

(1)  By  a  guard  of  observation,  stationed  above  the  bridge,  pro- 
vided with  boats  containing  anchors,  grapnels,  hammers,  chains, 
etc.  The  object  may  be  turned  ashore,  or,  if  this  is  not  possible, 
an  anchor  may  be  attached  to  it  to  break  its  momentum. 

(2)  By  a  floating  stockade,  constructed  of  trees  united  by  chains 
and  forming  a  continuous  barrier  to  floating  objects.  Its  direc- 
tion should  be  about  20°  with  the  current. 

(3)  By  constructing  the  bridge  by  rafts  and  withdrawing  the 
menaced  part,  thus  allowing  the  object  to  float  past. 


C  llAPTER  XVII.-Koads. 


353. — The  frequent  necessity,  in  the  field,  for  the  construction 
of  a  short  piece  of  road,  or  the  repairing  of  existing  roads,  makes 
it  important  that  all  who  may  at  any  time  have  this  work  in 
charge  should  be  familiar  with  the  principal  requirements  of  it. 

354.— Two  desirable  conditions  in  a  road  are  that  it  be 
straight  and  level ;  where  both  cannot  be  obtained,  straightness 
is  sacrificed  to  levelness.  Other  things  being  equal,  the  length  of 
a  road  may  often  be  advantageously  increased  20  ft.  for  every  foot 
of  vertical  height  avoided. 

355. — liiniiting;  Gradient.  As  levelness  cannot  always  be 
obtained,  various  considerations  fix  limits  for  the  steepness,  called 
limiting  gradients,  which  are  to  be  used  only  when  unavoidable; 
thus,  for  a  very  short  distance,  as  an  approach  to  a  bridge,  the 
limiting  gradient  may  be  j^ ;  a  grade  of  ^^  should  not  exceed  100 
ft.;  one  of  -^  should  not  exceed  200  ft.;  2^0  should  ordinarily  be 
the  limiting  gradient  for  easy  travel,  while  Jg  to  ^5  is  still  better. 

356. — Compared  to  what  he  can  draw  on  a  level,  a  horse  can 
draw  only  about  90%  on  a  grade  of  jJo?  80%  on  ^^5  ^0%  on  ^^,  and 
25%  on  jS,  but  for  a  short  distance  he  can  exert  6  times  his  ordi- 
nary force. 

357. — A  road  should,  if  possible,  always  rise  continuously  to 
its  highest  point  and  nowhere  descend  partially  again. 

358. — Widtli.  For  military  purposes  roads  should  be  wide 
enough  to  allow  wagons  going  in  opposite  directions  to  pass  each 
other  easily;  this  is  usually  taken  at  16  ft.  For  wagons  going 
in  one  direction  only  or  with  turnouts  at  intervals,  and  for  infan- 
try in  column  of  fours,  or  cavalry  in  column  of  twos,  9  ft.  will  suf- 
fice, and  for  pack  animals  6  ft.  At  turns  in  a  zig-zag  road  up  a 
hill  the  road  should  be  level  and  the  width  increased  from  J  to  |. 


PLATE  50. 


-3fvet 


.  Hadadani 


^l^^  /GAtcle 


£JjJ 


Roads.  215 

359. — Form.  The  best  for  the  upper  surface  is  that  of  two 
planes  inclined  at  an  angle  of  about  ^^  and  joined  by  a  slight 
curve  5  ft.  long.     (PL  50,  Figs.  1,  2  and  13.) 

Between  the  road  and  ditches  should  be  flat  mounds  raised  6 
in.  or  more  above  the  surface  with  sloping  sides  covered  with 
sods  or  stone  next  to  road,  forming  with  roadway  the  gutters; 
they  serve  also  to  hold  up  the  road  material  and  as  warnings  at 
night  of  the  proximity  of  the  ditch. 

On  a  hill  side  the  surface  should  be  a  single  plane  inclined 
towards  the  hill.     (Figs.  3,  4,  5,  7  and  8.) 

360. — Road-bed.  The  surface  of  the  road-bed  should  be 
dug  out  or  built  up  and  solidly  compacted,  either  by  rolling  or 
ramming,  and  when  ready  to  receive  the  road  material  should  be 
of  the  same  shape  as  the  surface  of  the  finished  road,  with  shoul- 
ders at  the  sides  to  retain  the  material  in  place.     (Fig.  13.) 

On  hillsides  of  gentle  slope,  the  road-bed  is  usually  made  of 
half  cutting  and  half  filling,  the  lower  side  of  the  slope  being 
stepped  to  retain  the  earth  excavated,  (Fig.  3);  on  steep  slopes  it 
is  often  necessary  to  both  step  the  slope  and  build  a  retaining 
wall  of  stone,  (Fig.  4);  or  of  logs,  (Fig.  5);  or  of  other  materials;  on 
very  steep  slopes  it  may  be  necessary  to  build  retaining  walls  on 
both  sides,  (Fig.  7);  while  in  rocky  formations  the  excavated  hill- 
side may  be  left  nearly  vertical,  (Fig.  8.) 

361. — Drainage.  Nothing  is  of  greater  importance  in  road 
building  than  proper  drainage.  It  is  the  life  of  a  road.  In  a 
level  country  it  is  necessary  to  raise  the  road-bed  to  keep  it 
always  free  from  water.  None  must  be  allowed  to  remain  on  the 
surface  and  all  must  be  drained  from  beneath.  To  accomplish 
this  ditches  must  be  dug  on  both  sides  of  a  road  on  level  ground 
and  in  cuttings,  from  2  to  3  ft.  below  the  road-bed  and  of  a  width 
depending  on  the  amount  of  water  to  be  discharged.  (Figs.  1  and 
2.)  In  wet  places,  low-lying  lands,  clayey  and  springy  soils,  the 
ditches  must  be  deeper  and  sub-drains  3  to  5  ft.  below  the  road, 
emptying  at  intervals  into  the  side  ditches,  must  be  made  to  keep 
it  dry.     (Fig.  1.) 

Rain  falling  on  the  surface  of  the  road  is  collected  in  the  gut- 
ters on  the  sides  and  run  into  the  side  ditches  by  drains  at  fre- 
quent intervals. 

On  a  hillside,  between  the  road  and  the  hill  is  the  ditch,  from 
which  the  water  is  discharged  through  culverts  or  covered  drains 


k 


21G  Roads. 

under  the  road  into  the  natural  watercourses.  Catch  drains 
along  the  top  of  the  cutting  are  made  to  prevent  the  slopes  being 
washed  down  and  the  water  from  above  finding  its  way  to  the 
road. 

Where  open  ditches  are  liable  to  become  filled,  some  kind  of 
covered  drain  must  be  used.    (Pigs.  5,  10, 11  and  12.) 

Theoretically,  a  road  should  be  perfectly  level,  but  for  purposes 
of  drainage,  in  the  direction  of  its  length,  it  should  have  at  least 
a  slope  of  ilg. 

On  a  steep  road,  shallow  paved  water  tables  extending  obliquely 
across  the  road  are  sometimes  necessary  to  catch  the  water  run- 
ning down  the  road  and  carry  it  to  the  gutters,  or  small  mounds 
crossing  the  road  obliquely  are  substituted.     (Fig.  9.) 

362. — The  surface  of  a  road  ought  to  be  as  smooth  and  as 
hard  as  possible,  for  which  purpose  various  kinds  of  covering  ma- 
terial are  put  on  the  bed. 

As  the  roadbed  must  be  kept  thoroughly  dry  at  all  times  by  the 
ditches  intercepting  all  ground  water,  so  the  stone  or  other  cover- 
ing must  be  so  thoroughly  rolled  and  compacted  that  no  water 
falling  upon  the  surface  can  possibly  find  its  way  down  to  the 
foundation  and  through  it  to  the  bed. 

3 03, — When  roads  are  made  of  broken  stone  the  material  in 
the  Telford  class  is  composed  of  two  parts:  the  foundation  and 
the  covering.  (Fig.  1,  right  half.)  The  foundation  consists  of  a 
uniform  thickness  of  not  less  than  5  in.  of  any  durable  broken 
stone  with  bases  about  5  in.  x  10  in.  laid  close  together  by  hand, 
larger  faces  down,  firmly  wedged  with  smaller  stones  in  the  inter- 
stices, and  the  whole  sledged  and  rolled  to  a  uniform  surface. 
Then  a  thin  layer  of  binding  material,  as  clay  or  loam,  is 
sprinkled  over  it  and  rolled.  On  this  is  put  the  covering  consist- 
ing of  a  layer  of  about  3  in.  of  broken  stone  of  uniform,  well 
shaped  cubical  pieces  which  will  pass  through  a  ring  from  2  to  2^ 
in.  in  diameter,  and  rolled  to  a  uniform,  compact  surface.  Then 
another  layer  of  binding  material  is  added  and  well  rolled. 
Another  layer  of  stones,  3  in.  thick,  of  sizes  from  1  to  2  in.  in  dia- 
meter is  next  spread  and  rolled  as  before.  On  this  may  be  spread 
another  binding  coat,  well  rolled,  then  a  thin  layer  of  fine  screen- 
ings or  fine  gravel  free  from  dirt.  Often,  where  traffic  is  light  and 
expense  large,  a  single  layer  of  broken  stone  4  in.  thick  is  put  on 
the  foundation. 


Roads.  217 

3()4.— In  the  Macadam  class  (Fig.  1,  left  half)  the  hand-laid 
foundation  is  not  used,  but  generally  three  layers,  each  from  3  to 
4  in.  thick,  of  broken  stone  and  binding  coats,  as  described  above, 
are  spread  and  rolled  until  smooth  and  compact. 

For  light  traffic  a  single  layer  of  4  in.  is  sometimes  used. 

305.  The  best  stone  is  a  compact,  tine-grained  syenite,  basalt 
or  trap  rock.  Hornblend,  actinolyte,  dioryte,  and  some  other 
rocks  make  good  material.  Quartz  and  flint,  though  very  hard 
are  brittle,  difficult  to  work,  and  not  so  good.  Granite,  on  ac- 
count of  mica  in  it,  breaks  up  and  grinds  away  too  easily.  Gneiss 
is  poorer  than  granite.  Slatey  rocks  generally  break  up  too  easily. 
Limestone,  generally  too  soft,  grinds  away  easily,  making  a 
very  disagreeable  dust.  Softer  stones  may  be  used  for  the  foun- 
dations and  lower  layers  but  only  the  hardest  and  toughest  should 
be  used  for  the  coverings. 

3G6. — Earth  roads  require  even  greater  care  in  draining, 
grading,  and  forming  the  surface  than  those  described,  and  a 
transverse  slope,  not  less  than  g^)?  to  hasten  the  flow  of  surface 
water  to  the  gutters.  No  sods  or  vegetable  refuse  should  be  al- 
lowed in  grading  or  filling  ruts,  but  gravelly  earth,  if  obtainable. 

Roads  are  frequently  made  with  a  metal  portion  in  the  center 
and  earth  roads,  called  ivings,  on  the  sides.   (Fig.  2.) 

307. — It  is  almost  impossible  to  construct  a  road  of  clay  which 
will  be  good  in  wet  weather,  but  a  very  sandy  road  may  be  im- 
proved by  working  a  little  clay  in  it. 

308.— For  gravel  roads  the  bed  is  first  formed  as  described. 
The  gravel  is  screened  to  remove  stones  larger  than  2|  in.  in  dia- 
meter and  such  as  are  less  than  f  in.;  and  all  earthy  matter.  A 
layer  of  the  screened  gravel,  4  or  5  in.  thick,  is  then  spread  and 
rolled,  then  another  layer  of  3  or  4  in.  which  should  also  be  well 
rolled. 

309. — Kei^airs.  Ruts  appearing  should  be  immediately 
filled  in,  and  traffic  directed  over  all  parts  of  road.  Before 
spreading  stones  all  mud  should  be  cleaned  off  and  the  surface 
picked  up  a  little  to  allow  the  new  stone  to  bind  into  the  old,  wet 
weather  being  preferred,  or  the  stones  should  be  sprinkled. 
Ditches  and  culverts  must  be  cleaned  as  needed. 

3 TO. — In  crossing  marshy  ground  that  cannot  be  well  drained, 
logs  of  suitable  lengths  laid  side   by  side  across  the  road,  over 


218  Roads. 

which  is  spread  a  covering  of  earth  or  gravel,  are  sometimes 
used. 

371. — Brushwood,  made  into  fascines  and  hurdles,  may  be 
used  the  same  way  as  a  foundation.  With  fascines,  the  top  row 
should  extend  across  the  road  and  be  of  a  length  equal  to  the 
width  of  road.     (Fig.  G.) 

372. — Where  lumber  is  the  cheapest  material,  plank  roads 
may  be  built  by  first  laying  parallel  rows  of  sleepers  or  sills  flush 
with  the  ground,  about  4  ft.  apart,  in  the  direction  of  the  road,  on 
which  boards,  3  in.  thick  by  9  to  12  in.  wide  and  8  ft.  long,  are 
placed  crosswise. 

373.— The  construction  of  communications  to  all  parts  of  a 
position  to  facilitate  the  movement  of  troops,  etc.,  from  one  part 
to  another,  is  almost  always  a  certain  necessity.  These  would 
rarely  be  more  than  temporary,  but,  if  made  on  the  lines  indi- 
cated, as  far  as  time  and  requirements  permitted,  so  much  the 
better. 

374. — Roads  and  paths  may  have  to  be  cleared  through  woods; 
wet  places  made  passable  by  corduroying  or  filling  up  with  brush, 
fascines,  etc.;  and  approaches  made  to  ascend  steep  places. 

Wherever  roads  cross  or  separate,  signs  should  be  put  up  telling 
exactly  where  each  leads. 


PLATE  51 


FIG.l, 


FIG.  2. 


F'SH    PcAre 


D         D         D         d         D         n 


\/'ySH  PtATes 


^^^^  (f^^\ 


IT 


^  ^^o 


FIG  3        //art/brd  Bessed  Steel  lie 

FIG.  4. 


EIG5: 


J^einfifj'ced         \\j  .     V 


w 


FIG.8. 


InterUdcing bolis  FIG.7 
FIG.9. 


1 


=? 


DOUBLE   CIHO 


a^     \_/m^. 


FIG.  10 


iia 

n  n 

H. 

Fl.  f^ 

.fi. 

If  [1  ii. 

J- 

iy~' 

Ti 

b1 

iL 

n 

11' 

10"  y 

■y 

i^    TZi — mr-* 

jStub  su/iiph        @-= 


FIG  11. 


FIG.12, 


CHAPTER  XYIII.— Railroads. 


375. — In  military  operations,  the  principal  duties  of  troops  in 
connection  with  railroads  will  be  either  the  repairing  of  lines  that 
have  been  partially  destroyed,  or  the  destruction  of  lines  to  pre- 
vent their  use  by  the  enemy. 

376.— A  railroad,  as  existing  in  its  completed  form,  will  be 
briefly  described  to  indicate  the  state  to  which  it  should  be 
brought  by  repairs  after  destruction,  and  to  so  familiarize  one 
with  it  as  to  suggest  methods  of  most  effectually  destroying  it. 

.377. — A  railw^ay  line  consists  of  a  series  of  straight  lines  of 
different  lengths,  called  tangents,  which  are  joined  by  curves. 
The  roadbed  is  first  prepared  with  a  smooth  hard  surface  (sloping 
slightly  from  the  middle  to  each  side  for  drainage)  from  10  to  12 
ft.  wide  for  a  single  track,  and  from  21  to  25  ft.  for  a  double  track. 
On  this  is  placed  the  ballast,  from  12  to  24  in.  thick,  of  broken 
stone,  gravel  or  cinders,  etc.,  for  the  purpose  of  distributing  the 
load  over  a  larger  surface,  holding  the  ties  in  place,  carrying  off 
the  rainwater,  affording  a  means  of  keeping  the  ties  up  to  grade 
line  and  giving  elasticity  to  the  roadbed. 

.378. — The  ties  are  generally  of  wood,  hewn  flat  on  top  and 
bottom,  from  7.5  to  9  ft.  long,  6  to  10  in.  wide,  and  about  7  in. 
deep.  It  is  customary  to  sink  them  about  half  their  depth  into 
the  ballast.  Their  object  is  to  hold  the  rails  in  place  and  furnish 
an  elastic  medium  between  the  rails  and  ground.  The  distance 
apart  is  usually  2.5  ft.  from  center  to  center,  but  depends  upon 
weight  of  engines  and  strength  of  rails.  They  should  be  uni- 
formly spaced  to  distribute  the  weight  equally. 

Tie  plates  (PI.  51,  Figs.  3  and  7)  are  often  used  to  prevent  the 
rails  from  crushing  into  the  ties. 

.379. — Tests  of  metal  ties  in  the  interests  of  economy  and  effi- 
ciency have  been  made  with  satisfactory,  results.  On  some  level 
portions  of  the  N.  Y.  Central  R.  R.  are  used  the  Hartford  pressed 


222  Railroads. 

steel  tie  (Pigs.  1  and  2),  to  which  the  rails  are  fastened  by  clamps 
bolted  to  the  tie. 

380. — The  form  of  rail  used  in  the  United  States  is  shown  in 
Fig.  3,  being  the  "T"  rail,  which  varies  in  weight  from  12  to  100  lbs. 
per  yard.  The  mean  dimensions  of  80  lb.  rails  are  given  on  left 
hand  side  of  figure  and  of  100  lb.  rails  on  right  hand  side.  They 
are  placed  3  ft.  apart  for  narrow  gauge,  4  ft.  8.5  in.  for  standard 
gauge,  while  6  ft.  is  the  broadest  gauge  in  the  U.  S.,  measured 
from  inside  to  inside  of  head.  The  tops  of  rails  must  be  slightly 
inclined  to  fit  the  cones  of  the  wheels. 

381. — The  weak  part  of  a  track  is  at  the  joints.  The  old 
method  of  using  chairs  under  the  ends  of  rails  has  about  ceased, 
the  practice  now  being  to  fish  the  joints  by  plates  (Pig.  1),  and 
angle  irons.  (Pig.  3.)  There  are  also  used  what  are  known  as 
the  Reinforced  rail  joints  (Pig.  4),  Bridge  rail  joints  (Pig.  8), 
Double  Girder  rail  joints.     (Pig.  9.) 

382. — Rails  are  fastened  to  the  ties  by  spikes,  the  best  being 
made  with  sharp,  chisel-edge  points,  clean,  sharp  edges,  and 
smooth  surfaces,  so  as  to  cut  and  press  aside  the  fibers  of 
the  wood,  instead  of  tearing  them.  Attempts  to  increase  the 
holding  power  by  jagged  or  twisted  spikes  have  been  unsuccess- 
ful. On  bridges,  interlocking  bolts  (Pig.  6)  are  much  used  instead 
of  spikes.  To  keep  the  track  in  the  right  line,  allowance  must  be 
made  for  the  contraction  and  expansion  of  the  rails,  by  not  plac- 
ing them  in  contact  at  the  joints,  and  the  holes  for  the  bolts  must 
be  elongated. 

383. — The  centrifugal  force  of  a  train  passing  around  a  curve 
tends  to  throw  the  wheels  against  the  outer  rails,  which  is  par- 
tially counteracted  by  raising  them  to  throw  the  center  of 
gravity  inward  and  cause  the  car  to  slide  inward.  Each  rail  in  a 
curve  ought  to  be  bent  to  fit  the  curve  before  being  laid. 

384. — On  single  tracks,  there  are  laid  at  occasional  intervals 
short  pieces  of  track,  called  sidings,  to  enable  trains  to  pass  one 
another.  The  arrangement  for  passing  from  one  track  to  another 
is  the  switch,  which  consists  of  a  single  length  of  rails,  movable  at 
one  end  by  a  lever,  so  as  to  connect  with  either  pair  of  rails.  The 
simplest  form  is  the  stub  switch  (Pig.  10),  which  leaves  one  line 
always  open  while  the  other  is  continuous.  The  one  in  common 
use  is  the  split  or  point  switch  (Pig.  11.)  Various  devices  are 
used  for  locking  and  interlocking  switches,  to  avoid  accidents. 


tlNlVEBSlTTi' 


PLATE  52.  - 


Railroads.  225 

At  the  points  where  the  inner  rails  cross  is  placed  a  frog  (PI.  52, 
Fig.  1),  which  enables  the  wheels  to  pass  over  the  inner  rail  of 
the  other  track. 

385. — Crossings  occur  where  two  tracks  intersect,  and  consist 
of  four  frogs  and  corresponding  guard  rails.    (PI,  51,  Fig.  12.) 

386. — Where  one  main  line  passes  to  another  is  called  a  junc- 
tion and  the  ordinary  switch  is  used.  In  crossing  from  one  track 
to  a  parallel  track  the  rails  are  arranged  as  in  PI.  52,  Fig.  2. 

387. — A  wye,  from  a  similarity  to  the  l^etter  "Y,"  isjan  arrange- 
ment of  tracks  for  turning  around  engines  and  cars  and  connect- 
ing cross-roads.     (Fig.  3.) 

388. — Turntables  are  platforms,  turning  on  rollers  upon  an 
underground  circular  track,  used  to  transfer  engines  and  cars 
from  one  track  to  another  and  to  turn  them  around. 

389. — The  locomotive  engine  is  the  power  on  railroads.  They 
weigh  from  58,000  lbs.  to  190,000  lbs.  without  tender,  and  from  218,- 
(X)0  lbs.  for  passenger  to  310,000  lbs.  for  freight,  with  tender,  all 
loaded,  and  draw  2,400  or  morb  tons  on  a  level.  The  amount  of 
coal  consumed  being  from  40  lbs.  to  70  lbs.  per  mile  run. 

390. — The  rolling  stock  consists  of  passenger  cars  for  about  60 
persons,  48  to  52  ft.  long,  9.5  ft.  wide,  weighing  from  40,000  lbs.  to 
00,000  lbs.;  sleeping  cars  for  64  passengers,  60  to  70  ft.  long,  9.8 *ft. 
wide,  weighing  60,000  lbs.  to  90,000  lbs.;  mail,  express  and  bag- 
gage cars,  45  ft.  long,  9.3  ft.  wide,  weighing  about  27,000  lbs.; 
freight  cars  consist  of  Box,  Refrigerator,  Hay,  Furniture,  Oil, 
Stock,  etc.,  and  are  about  34  ft.  long,  8.5  ft.  wide,  weighing  about 
20,000  lbs.,  capacity  20  tons ;  fiat  cars,  34  ft.  long,  weigh  16,000 
lbs.  to  19,000  lbs.  Height  of  top  of  box  cars  above  rails  about  15 
ft.  Freight  cars  are  being  rapidly  provided  with  the  M.  C  B. 
automatic  couplers.     (Fig.  4.) 

391.^The  buildings  consist  of  passenger  and  freight  depots, 
engine  houses,  fuel  sheds,  water  tanks,  repair  shops,  and  section 
houses.  At  convenient  points  are  generally  located  yards  where 
stock  can  be  loaded  and  unloaded.  It  may  sometimes  be  neces- 
sary, however,  to  load  and  unload  animals  and  supplies  in  the 
field  along  a  railroad  where  there  are  no  platforms  or  other  con- 
veniences, which  must  then  be  built. 

392. — A  siini)le  form  of  rani]), in  the  absence  of  anything 
better,  could  be  made  by  taking  3  or  4  i)lanks  3  in.  thick,  10  to  12 
in.  wide, and  10  to  14  ft.  long,  fastening  them  together  side  by  side, 


--<  >  Kailkoads. 

preferably  by  footholds  nailed  across  on  top,  and  several  cleats  on 
the  bottom ;  otherwise,  by  lashing,  wiring  or  by  stakes  at  the  bot- 
tom when  in  position,  and  wedges  in  the  car  door.  The  ends  on 
the  ground  should  be  slightly  sunken  and  rested  against  a  cross 
beam.  Ropes  should  be  hung  along  the  sides  and  blankets  or 
canvas  hung  on  them.  Props  of  some  kind,  as  sacks  of  grain, 
bales  of  hay,  etc.,  can  be  placed  under  the  middle  to  strengthen 
it  if  necessary. 

.393. — Another  form  of  jmrtahJe  tamp,  which  could  be  carried 
on  all  railroad  trains  where  they  might  be  needed,  consists  of  G 
long  timbers  4  in.  x  4  in.  x  14  ft.,  6  short  timbers  4  in.  x  4  in.  x  G 
ft.,  24  boards  1.5  in.  x  12  in.  x  G  ft.  with  footholds  nailed  length- 
wise on  one  side. 

To  load  or  unload  horses,  rest  the  ends  of  three  of  the  long  tim- 
bers, equally  spaced,  on  the  car  floor,  the  other  ends  resting 
against  a  short  timber,  sunk  in  the  ground  and  staked  down.  On 
these  place  the  boards  forming  the  floor;  on  each  side  of  the 
ramp,  on  the  boards,  lay  a  long  timber  and  fasten  the  ends  to  the 
timbers  underneath.  The  boards  should  have  cleats  on  under 
side  to  prevent  slipijing  sideways.  If  necessary,  some  of  the  re- 
maining boards  can  be  set  edgewise  between  posts  of  the  short 
timbers  as  an  intermediate  support. 

394. —  To  unload  amimherof  cars,  enough  men  can  be  placed 
under  the  ramp,  near  the  car,  to  raise  it  high  enough  to  allow  the 
car  to  be  removed  and  another  run  in  place,  thus  avoiding  tak- 
ing the  ramp  apart  for  each  car, 

395. — Semi-permanent  platforms  and  ramps  may  be  made  as 
in  Figs.  6  and  7,  if  rails  and  boards  are  available. 

396. — To  load  or  unload  ivagons  and  guns  from  a  flat  car, 
place  the  ramp  against  one  end  (Fig.  8),  using  four  long  timbers 
for  stringers  on  which  the  boards  are  placed,  the  other  two  long 
timbers  being  used  for  side  rails.  Support  underneath  with 
boards  set  on  edge,  held  between  some  short  timbers,  or  with 
bales  of  hay,  sacks  of  grain  or  otherwise,  as  necessary.  A  couple 
of  boards  can  be  used  to  run  the  wheels  from  the  car  on  to  the 
ramp  and  others  at  the  foot  of  ramp  to  carry  the  wheels  across 
the  rails.  The  lower  ends  of  the  stringers  should  abut  against  a 
tie,  if  possible ;  if  not,  they  should  be  staked  down. 

397. — PI.  53,  is  a  design  of  a  jjortable  ramp  devised  by  Major 
E.  G.  Fechetj  6th  U.  S.  Cavalry.     The  ramp  consists  of  7  boards 


PLATE  53. 


Major  E.C.FecHKT, 

6^  Cavalry. 
US.Anr^Y. 


F.A.f^.C.B: 


Railroads.  221) 

1.5  in.  X  7  in.  x  12  ft.,  joined  together  in  three  sections  (2  for  the 
outside,  "A,"  "A;"  and  3  for  the  middle  one,  "B");  by  wooden 
strips  "C,"  1  in.  thick,  and  2  in.  wide,  bolted  to  the  upper  surfaces, 
1  ft.  between  centers;  these  strips  also  serve  as  foot  holds.  Along 
the  middle  of  the  outside  boards  extends  a  side  rail,  "D,"  3  in.  x 
3  in.  held  firmly  by  the  iron  straps,  "E,"  ^  in.  x  2  in.  On  the  out- 
side of  each  side  rail  are  3  sockets  "P,''  for  standards  "G"  3  ft. 
high,  along  the  tops  of  which  are  to  be  stretched  ropes  or  chains 
from  which  canvas  or  blankets  are  hung.  On  the  under  side  of 
each  section  3  ft.  apart  are  bolted  iron  cleats,  "H,*'  0.5  in.  x  2  in., 
beginning  at  18  in.  from  the  ends.  On  the  ends  of  each  section  are 
bolted  iron  claws,  "K,"  for  catching  the  car  floor  or  door  slide,  to 
prevent  slipping  when  in  position  for  use.  The  three  sections  are 
held  together  for  use  by  4  iron  tie  bars,  "L,"  0.5  in.  x  2  in.  which 
are  placed  under  the  cleats  "H,"  and  the  whole  firmly  keyed  as 
shown.  This  form  of  ramp  may  be  made  longer  or  shorter,  nar- 
rower or  broader,  as  desired.  By  taking  out  the  standards  it 
may  be  hung  on  the  side  of  a  car  between  a  door  and  end.  It 
is  easily  taken  apart  and  transported  in  a  wagon,  and  as  easily 
put  together  when  needed.  It  is  designed  to  combine  both 
strength  and  liglitness.    It  weighs  about  400  lbs.  complete. 

31)8. — Disabling  and  destroying  railroads.  Under  the 
head  of  disabling  will  be  mentioned  means,  the  effects  of  which 
will  only  temporarily  interrupt  traffic,  can  be  easily  repaired,  but 
will  cause  delays. 

399. — Under  destroying,  such  as  are  more  serious  in  their 
effects:  either  causing  extensive  repairs  or  a  change  of  route  to 
avoid  them. 

400. — The  disabling  of  railroads  will  usually  be  done  by  raid- 
ing parties  of  cavalry,  while  the  destroying  of  them  may  be  done 
by  such  parties  or  specially  detailed  troops  trained  for  such 
service. 

401 . — It  must  be  understood  that  no  railroad  is  to  be  destroyed 
except  upon  the  orders  of  the  officer  commanding  in  the  field. 
If  otherwise,  and  it  should  be  taken  from  the  enemy,  the  dam- 
age done  might  seriously  embarrass  future  operations.  Before 
ordering  any  destruction  the  quesiton  will  arise^"  Is  destruction 
absolutely  necessary  ?"  "Will  it  be  of  no  further  use  and  is  every 
hope  of  regaining  it  gone  ?"  "  Are  the  advantages  to  be  gained 
sufficient  to  compensate  for  the  damage  that  will  be  done  ?"     All 


II.'JO  Kailkoads. 

the  attending  circumstances  should  be  carefully  considered, 
especially  if  in  one's  own  country.  The  choice  of  points  for  de- 
struction and  the  most  effective  means  are  subjects  for  study.  It 
is  useless  to  destroy  anything  that  will  not  seriously  embarrass 
traffic. 

402. — A  railroad  may  be  disabled  by  removing  rails  at 
various  intervals,  then  destroying  or  hiding  them  ;  or,  if  a  large 
number  of  men  are  at  hand,  select  a  high  embankment,  line  the 
men  along  on  one  side  of  the  track,  disconnect  the  rails  at  each 
end  of  the  line  of  men,  then,  at  a  signal,  they  raise  the  track  on 
edge  and  let  rails  and  ties  together  go  over  the  embankment. 
Thus  treated,  rails  and  ties  must  be  separated  before  being  re- 
placed. An  improvised  wrench  for  removing  nuts  on  fish  plates 
is  a  bolt  with  two  nuts  on  it,  just  far  enough  apart  to  grasp  the 
nut  to  be  removed.  (PI.  52,  Fig.  5.)  If  time  is  an  object,  remove 
outside  rails  on  a  curve,  or  disconnect  a  joint  on  each  side  and 
throw  them  as  a  switch  to  derail  the  train  either  on  an  embank- 
ment or  in  a  cut,  or  use  explosives  as  described  in  Chap.  XX. 

By  laying  rails  across  a  pile  of  burning  ties  until  red  hot  in  the 
middle  they  may  be  easily  bent  around  a  tree  or  telegraph  pole  ; 
they  may  be  twisted  by  heating,  as  above,  then  using  bars  or  pick 
axes  placed  in  the  holes  in  each  end  and  working  in  opposite 
directions. 

They  may  be  torn  from  the  ties  and  twisted  cold  by  using  Gen. 
Haupt's  "U  "shaped  rail  twister,  shown  on  PI.  40,  Fig.  8.  Ten 
men  with  two  twisters,  two  axes,  two  stout  pieces  of  rope  35  ft. 
long,  can  tear  up  and  twist  a  rail  in  5  minutes.  The  junctions  of 
lines  are  important  points  to  attack  to  disable  a  track. 

Water  tanks  may  be  rendered  useless  for  a  time  by  breaking 
holes  in  them,  removing  pistons  from  pumps,  etc.  Fuel,  ties,  and 
small  bridges  may  be  burned.  Engines  may  be  disabled  by  burn- 
ing out  the  flues,  removing  or  breaking  different  parts  of  the  ma- 
chinery, tilling  suction  pipes  of  pumps  with  waste,  etc.  Cars  may 
be  disabled  by  removing  couplers,  axle  boxes,  breaking  or  remov- 
ing trucks,  etc.  The  use  of  mines  under  the  track,  so  arranged 
as  to  be  exploded  by  the  passing  of  trains,  is  an  effective  method 
of  interrupting  traffic  and  shaking  the  morale  of  troops  being 
transported. 

403. — To  destroy  a  railroad,  if  time  is  sufficient,  remove  roll- 
ing stock,  rails,  etc.,  to  the  rear.  Otherwise,  destroy  large  bridges, 


Railroads.  231 

if  of  wood,  by  burning,  using  oil  if  it  can  be  obtained,  or  by  explo- 
sives, as  in  Chapter  XX.  If  of  iron,  steel,  or  masonry,  by  ex- 
plosives, as  in  Chapter  XX.  If  there  are  tunnels  on  the  line, 
select  longest  ones  and  blow  them  in  at  as  many  points  as  possi- 
ble, or  cause  two  wild  trains  to  collide  in  the  middle,  afterwards 
blowing  in  the  ends.  Those  with  sandy  soil  are  the  best.  Deep 
cuttings  with  retaining  walls  may  be  filled  in  by  use  of  explo- 
sives. If  trees,  poles,  wires,  etc.,  can  be  mixed  in — so  much  the 
better.  Blow  up  tanks  and  engines,  burn  all  fuel,  cars,  repair 
supplies,  etc.    Fire  a  cannon  ball  through  engines. 

404.— The  repair  of  railroads  will  best  be  accomplished 
by  a  construction  corps  having  some  of  the  elements  of  perma- 
nency in  its  organization;  or,  at  least,  by  small  squads  of  exper- 
ienced men  to  which  others  could  be  added  by  temporary  detail, 
whenever  active  operations  require  such  increase.  They  should 
be  established  as  near  to  where  their  services  may  be  needed  as 
possible. 

405. — Bridges  should,  in  the  beginning,  be  classified  and 
numbered,  so  that  a  single  reference  to  the  class  and  number  will 
give  complete  information  as  to  its  character,  dimensions,  etc.  At 
designated  points  will  be  kept  on  hand,  already  prepared  for  put- 
ting in  bridge,  suitable  materials  for  the  repair  of  each  class. 
This  was  done  by  the  Union  Army  from  1861  to  1865,  so  that, 
when  word  was  received  that  a  certain  bridge  had  been  destroyed, 
by  a  reference  to  the  class  and  number  the  reconstruction  corps 
started  out  carrying  with  it  just  what  was  needed  to  repair  the 
bridge.  Even  complete  trusses  for  the  larger  class  of  bridges 
were  prepared  and  kept  ready  for  use. 

406. — Tunnels  and  cuts  which  have  been  filled  up  can  gener- 
ally be  cleared  only  from  the  two  ends. 

40T. — Rails,  fish  plates,  spikes,  ties,  etc.,  will  be  kept  in  store 
at  secure  places,  for  repairing  any  portions  of  destroyed  track. 
Rails  which  have  been  simply  bent  can  be  straightened  by 
various  means.  Gen.  Haupt'S  method  was  as  follows:  Two 
ties  were  placed  on  the  ground,  across  these  two  more  ties  and  on 
top  a  single  tie  which  was  cut  across  one-half  the  depth  of  the 
rail  to  receive  it  and  prevent  it  turning.  Weight  was  applied  at 
the  two  ends  of  the  rail  by  men  bearing  down  on  poles  placed 
thereon.  The  rail  being  moved  back  and  forth  until  straightened, 
requiring  from  4  to  5  minutes.    Rails  which  had  been  heated  and 


232  Railkoads. 

bent  to  a  very  sharp  angle  required  more  time,  necessitating  re- 
heating and  hammering  until  straightened.  For  this  purpose,  at 
special  points  were  prepared  furnaces  consisting  of  two  parallel 
walls  of  brick,  stone  or  clay,  with  a  kind  of  grate.  The  straight- 
ening table  consisted  of  a  large,  square  timber  as  long  as  a  rail,  on 
which  were  securely  fastened  three  rails,  as  in  PI.  52,  Fig.  9  on 
which  the  heated  rail  was  laid  and  hammered  until  straightened. 
Twisted  rails  require  re-rolling  before  they  can  be  again  used. 


PLATE  54. 


CHAPTER  XIX.— Telegrapli  and  Teleplioiie  I^iiies. 


408.— In  order  that  telegraphic  messages  may  be  sent  from 
one  point  to  another,  it  is  necessary  that  there  be  a  continuous 
metallic  conductor  from  the  first  to  the  second  point  and  that  this 
conductor  be  insulated  from  contact  with  the  ground  or  with  any- 
thing leading  to  the  ground.  The  conductor  used  in  construct- 
ing permanent  lines  is  of  galvanized  iron  wire,  generally  of  size 
No.  9.  In  military  lines  it  is  generally  somewhat  smaller  on  ac- 
count of  the  weight.  The  wire  is  carried  on  poles  and  tied  to  glass 
insulators  which  are  attached  to  the  poles. 

409. — Poles  should  be  not  less  than  22  feet  in  length  nor 
less  than  7  and  5  inches  in  diameter  at  the  larger  and  smaller 
ends  respectively  and  should  be  stripped  of  bark  and  pointed  at 
the  upper  end.  The  holes  for  poles  should  be  not  less  than  |  the 
length  of  the  pole  in  depth.  The  poles  should  be  raised  as  shown 
in  PI.  54,  Fig.  1  and  held  vertically  while  the  excavated  earth  is 
thoroughly  tamped  in  from  bottom  to  top  ;  after  the  hole  is  com- 
pletely filled  the  earth  should  be  made  into  a  small  mound  so  as 
to  shed  water. 

410. — When  the  brackets  are  attached  to  the  pole  directly,  a 
seat  should  be  cut  in  the  pole  with  a  hatchet  and  the  bracket 
should  be  nailed  on,  using  1  twenty-penny  and  1  forty-penny  nail. 
Where  the  poles  are  intended  to  carry  several  wires,  cross-arms 
are  bolted  to  the  poles,  fitting  into  seats  cut  for  them.  The  arms 
carry  brackets  not  less  than  15  in.  apart.  The  arms  should  not 
be  less  than  20  in.  from  one  another.  Not  less  than  25  poles  to 
the  mile  should  be  used,  and  in  special  cases  the  number  may  be 
increased  to  30. 

411. — Every  5th  pole  should  be  protected  from  lightning  dis- 
charges by  having  a  piece  of  line  wire  run  from  about  6  in.  above 
the  top  of  the  pole  to  the  ground.    This  wire  must  he  so  arranged 


2^56  TeLFXIR APU   AND  TELEPHONE  LiNES. 

that  it  cannot  come  in  contact  with  the  line  wire  should  that  be- 
come unfastened.  Poles  should  be  vertical  except  when  neces- 
sary to  incline  them  to  resist  strains,  when  they  will  be  set  at  a 
slight  inclination,  in  such  manner  that  the  component  of  the 
strain  in  the  direction  of  the  length  of  pole  will  tend  to  press  it 
into  the  ground.  Where  exposed  to  great  strains,  or  to  contin- 
uously high  winds,  it  may  be  necessary  to  guy  the  poles:  this  is 
done  with  stays  consisting  of  two  or  more  line  wires  twisted  to- 
gether and  fastened  near  the  top  of  the  pole,  the  ground  end  being 
attached  to  a  section  of  a  pole  or  timber  suitably  anchored  in  the 
ground,  as  shown  in  Fig.  2.  Where  possible,  the  line  of  poles 
should  be  run  on  one  side  of  the  road  and  far  enough  from  it  to 
be  safe  from  accidental  damage  by  passing  wagons.  Where  roads 
have  to  be  crossed,  the  wire  should  be  carried  over  on  high  poles 
so  as  to  clear  any  possible  wagon  load. 

412. — The  insulators  in  common  use  in  this  country  are  of 
glass  and  of  the  form  shown  in  Fig.  3.  The  one  shown  in  Fig.  4 
is  preferable,  as  it  is  not  so  liable  to  cause  leaks  on  account  of 
moisture  accumulating  and  forming  a  connecting  film  to  the 
bracket  and  from  that  to  the  pole. 

413. — The  wire  is  attached  to  the  insulators  by  pieces  of  wire 
called  ties.  These  are  generally  of  the  same  wire  as  the  line. 
They  are  annealed  and  formed  on  an  insulator  and  cut  long  enough 
to  embrace  the  insulator  and  project  3  or  4  inches  beyond  the  line 
wire. 

414. — To  liaug  tlie  wire.  The  wire  is  carried  up  to  the 
top  of  the  pole  and  the  lineman  places  a  tie  on  the  insulator,  the 
line  wire  against  the  insulator  above  the  tie  wire,  and  bends  the 
ends  of  the  tie  wire  upward  so  as  to  sustain  the  line  wire.  The 
line  w^re  is  then  strained  by  the  lineman,  either  by  means  of 
hand  power  or  by  use  of  the  wagon  carrying  the  reel.  When  the 
ine  wire  is  stretched  so  that  it  sags  but  about  1}4  ft.  in  70  yds. 
the  tie  wire  is  wrapped  around  it  about  one  and  a  half  times,  finish- 
ing with  the  ends  of  the  tie  wire  pointing  towards  the  insulator  ; 
this  secures  the  line  and  completes  the  work.     (Fig.  5.) 

415. — 111  ojjeii  coiiiitry  the  line  wire  is  strung  on  the  in- 
sulator on  the  side  towards  the  pole,  so  that,  if  it  becomes  acci- 
dentally undone,  the  wire  will  not  drop.  If  in  timbered  country, 
then  hang  it  on  the  side  from  the  pole,  so  that  when  trees,  etc., 
fall  against  the  wire  it  will  simply  tear  it  away  from  the  insulator, 


Telegraph  and  Telephone  Lines.  237 

but  will  not  break  the  line  wire.  When  necessary  to  hang  the 
wire  on  trees,  a  regular  tree  insulator  should  be  used,  and  in  de- 
fault of  this,  the  tie  shown  in  Fig.  6  may  be  used,  the  ends  being 
wound  loosely  so  as  to  allow  of  an  easy  lateral  motion  to  accom- 
modate the  swing  of  the  tree.  The  poles  should  be  numbered  at 
each  mile  so  as  to  aid  linemen  to  report  location  of  breaks  and 
repairs. 

Streams  are  crossed  by  hanging  the  wires  on  strong,  high  sup- 
ports, taking  care  not  to  strain  the  wire  so  much  as  to  cause  it  to 
break. 

.  416. — The  description  of  instruments  and  batteries,  their  con- 
nections and  care,  will  be  found  in  the  Manual  published  by  the 
Signal  Service  of  the  Army. 

417. — Joints.  Where  wires  have  to  be  joined  to  preserve  the 
continuity  of  the  metallic  circuit,  the  best  joint  is  the  American 
twist  joint.  To  make  this,  clean  the  wires  for  a  length  of  5  or  6 
inches,  make  a  right  angle-bend  in  each  wire  about  4  inches  from 
the  end,  now  join  the  wires  so  that  the  ends  project  on  different 
sides  and  clamp  both  wires  with  a  hand  vise,  then  with  a  splicing 
iron  turn  the  ends  around  the  line  wire,  making  the  turns  as  close 
as  possible;  after  the  entire  end  is  turned  around  the  line  wire, 
cut  oif  the  projecting  end  and  dip  the  joint  into  melted  solder ; 
this  protects  the  joint  against  rusting.  The  details  of  this  joint- 
making  are  shown  in  Figs.  7  and  8. 

418. — Military  lines  are  generally  of  the  kind  designated  as 
flying  lines,  i.  e.,  they  are  intended  to  accompany  the  army  in  the 
field,  are  constructed  quickly  for  temporary  use,  and  are  as  quickly 
dismantled  and  taken  up.  The  poles  used  are  small  poles  called 
lances,  each  about  2J  in.  in  diameter  and  17  ft.  in  length,  placed  2 
ft.  in  the  ground,  and  run  about  40  to  the  mile.  The  batteries, 
line  lances,  and  instruments  are  carried  in  wagons  which  accom- 
pany the  army.  A  detailed  description  of  the  telegraph  with 
directions  how  to  erect  and  dismantle  is  found  in  the  Manual  of 
Signals  for  the  U.  S.  Army.  The  ordinary  telephone  receiver 
(with  magneto  call  bell)  is  used  on  the  military  lines;  but  for  the 
use  of  outposts,  reconnoiterers,  and  scouts,  a  special  form  of  tele- 
phone cart  and  wire  has  been  adopted,  the  following  description 
of  which  is  taken  from  the  Report  •  of  the  Chief  Signal  Officer  of 
the  Army,  1892: 


238  Telegkaph  and  Telephone  Lines. 

*'The  frame  of  this  cart  is  constructed  of  bicycle  tubing,  and  30 
in.  bicycle  wheels  with  heavy  cushion  rubber  tires  are  used.  The 
cart  is  fitted  with  an  automatic  spooling  device  for  reeling  up  the 
outpost  cable.  This  device  was  made  by  F.  S.  Cahill  &  Co.,  and 
is  a  success.  The  cart  carries  5  reels  of  cable  and  1  reel  knapsack 
for  use  in  places  where  the  cart  cannot  penetrate  owing  to  under- 
brush, etc.  As  the  extreme  width  of  the  cart,  measured  at  the 
wheels,  is  only  26  in.,  it  can  follow  any  ordinary  path  through 
underbrush.  The  weight  of  the  cart  complete  with  spooling  de- 
vice, but  without  the  reels,  is  only  53  pounds  ;  when  loaded  with 
reels  and  reel  knapsack  the  total  weight  is  157  pounds.  The  cart 
is  well  balanced  upon  its  axle  by  a  device  which  permits  the 
point  of  support  to  be  changed  to  balance  the  cart,  as  the  distri- 
bution of  the  weight  is  changed  by  the  cable  being  run  out.  In 
connection  with  the  reel  cart  a  telephone  kit  is  used,  and  by  at- 
taching the  double  connector  of  the  kit  to  one  on  the  frame  of 
the  cart  the  telephone  is  kept  in  circuit  and  conversation  can  be 
kept  up  with  the  home  station.  The  cart  with  its  load  can  be 
easily  drawn  by  one  man,  and  by  its  use  it  will  be  possible  to  con- 
nect outposts  with  the  main  guard,  or  brigade  with  regimental 
headquarters,  or  brigade  with  division  headquarters,  in  a  few 
minutes  of  time.  The  experience  of  the  English  in  Egypt  has 
proved  the  value  of  the  field  cable  line  in  action,  as  by  means  of 
these  lines  the  Commanding  General  was  kept  in  communication 
with  different  divisions  of  troops  and  with  those  actually  engaged 
in  the  firing  line.  It  is  proposed  to  fit  shafts  to  the  cart  so  that  a 
horse  can  be  harnessed  to  it,  thus  securing  great  rapidity  in  run- 
ning out  the  cable.  The  cart  carries  1§  miles  of  cable  which  can 
be  paid  out  as  fast  as  a  man  moves  with  the  cart,  and  by  means  of 
the  reeling  apparatus  and  spooling  device  can  be  recovered  at  the 
rate  of  4  miles  per  hour,  or  as  rapidly  as  a  man  can  walk  with  the 
cart." 

419. — Faults  are  generally  of  three  kinds — breaks  or  discon- 
nections, leaks  or  escapes,  and  crosses  or  contacts. 

Breaks  occur  when  the  metallic  circle  is  broken  or  cut  so  that 
either  the  disconnection  is  complete,  as  when  entirely  severed ;  or 
incomplete,  when  partially  cut  or  where  a  joint  is  rusted  so  much 
as  to  increase  the  conductive  resistance.  In  these  cases  the  in- 
struments will  work  weakly  or  fail  entirely. 


Telegraph  and  Telephone  Lines.  239 

[Leaks,  or  escapes.  Where  the  insulation  is  destroyed  or  is 
defective  or  where  a  wire  comes  in  contact  with  a  conductor  to 
the  earth  or  with  the  earth  itself,  a  portion  of  the  current  leaks  or 
escapes.  When  the  wire  is  swinging  the  leak  will  be  intermittent ; 
when  constant  leakage  is  going  on  the  instruments  will  work 
weakly ;  failing  altogether  when  the  leak  becomes  complete,  then 
it  is  called  a  ground. 

A  cross  occurs  when  two  wires,  each  carrying  currents,  are 
brought  into  contact;  thus  the  instruments  on  one  line  will  inter- 
fere with  the  workings  of  those  on  the  other.  Generally  occurs 
from  parallel  wires  being  swung  over  one  another  by  the  wind,  or 
having  a  good  conductor  fall  so  as  to  touch  both  wires. 

420. — Telegraph  lines  should  never  be  damaged  or  destroyed, 
except  in  obedience  to  direct  orders.  Faults  may  be  made  by  con- 
necting the  wires  together  with  small  wire  (this  makes  a  bad 
cross),  or  they  may  be  connected  with  the  lightning  rods  on  the 
poles,  thus  running  them  to  the  ground. 

When  an  office  is  taken,  the  instruments  should  all  be  discon- 
nected and  destroyed  or  taken  away ;  the  ends  of  the  wires  should 
be  tied  together.  The  batteries,  if  any,  should  be  disconnected. 
To  destroy  the  line,  cut  down  the  poles  and  burn  them  and  cut 
the  wire  into  small  lengths.  Subaqueous  lines  should  be  brought 
up  with  a  grapnel  and  a  piece  cut  out  and  cut  into  small  pieces 
and  thrown  back  into  the  water.  Subterranean  lines  are  gener- 
ally laid  in  conduits,  and  at  regular  intervals  man-holes  are  built 
to  allow  of  repairs ;  the  line  may  be  detected  by  these  man-holes, 
the  conduit  destroyed,  and  the  cables  disconnected. 


CHAPTEH  XX.— Demolitions. 


421.— In  military  practice,  demolitions  must  be  made  with  the 
least  possible  expenditure  of  time  and  explosive.  At  the  same 
time,  a  charge  which  in  itself  seems  large  for  a  particular  case 
may  prove  economical,  in  that  it  errs  on  the  right  side  and  a  repe- 
tition of  the  work  is  not  made  necessary. 

Military  engineers  have  to  destroy  bridges,  houses,  walls,  etc., 
render  roads  impassable,  fell  trees,  and  place  mines.  In  all  these 
operations,  high  explosives  are  generally  used,  on  account  of  their 
portability,  ease  of  handling,  and  great  destructive  effect.  In 
some  cases,  ordinary  gunpowder  is  available,  and  may  be  used  to 
advantage  if  time  allows  of  its  proper  placing  and  tamping.  Gun- 
cotton,  however,  is  the  standard  explosive  for  military  work,  and 
all  formulas  will  be  calculated  for  its  use. 

422. — (iuii cotton,  as  made  at  the  U.  S.  Naval  Torpedo  Sta- 
tion, is  in  blocks  about  3  in.  square  and  2  in.  thick,  each  block  be- 
ing i^erforated  to  allow  the  insertion  of  the  primer,  and  when  dry 
the  blocks  weigh  10  oz.  When  necessary  to  use  blocks  of  smaller 
dimensions,  the  large  ones  may  be  cut,  when  wet,  by  using  a  saw 
or  sharp  knife,  care  being  taken  to  place  the  block  to  be  cut  be- 
tween two  boards,  so  that  it  will  not  flake  or  crack  during  the 
operation.  Wet  guncotton  can  be  detonated  by  means  of  a  primer 
of  dry  guncotton.  Guncotton  will  absorb  about  30%  of  its  weight 
of  water,  and,  when  in  this  condition,  it  is  comparatively  safe,  as 
it  can  only  be  ignited  by  fire  and  is  difficult  of  detonation.  When 
packed  for  transportation,  the  blocks  are  placed,  while  wet,  in  a 
tin  can,  and  sealed  hermetically;  or,  the  can  is  left  so  that  the 
water  can  be  replaced  when  it  has  evaporated. 

423.— When  both  are  well  tamped,  guncotton  has  an  explo- 
sive force  from  2  to  2^^  times  as  great  as  gunpowder,  but  when  no 
tamping  is  used  it  has  a  force  4  times  as  great.    When  guncotton 


PLATE  55. 


Figu:re  1. 


Figure  2 . 


^ 


Figure 


Figure  4.  Figure 

6- 


Figure' 
8 


Demolitions.  243 

is  needed  for  use  as  primers,  a  sufficient  quantity  is  taken  from 
the  wet  case,  placed  in  the  sun,  and  allowed  to  dry.  In  operations 
in  the  field,  a  small  quantity  of  dry  guncotton  should  be  carried, 
so  as  not  to  waste  time  in  drying  the  primers.  Wet  guncotton 
detonates  with  much  greater  force  than  dry,  but  it  is  necessary 
that  this  action  be  set  up  by  the  detonation  of  a  dry  block  placed 
in  intimate  contact  with  the  wet  charge.  The  manner  of  firing 
guncotton  is  as  follows:— 

After  placing  the  explosive  in  as  close  contact  as  possible  with 
the  object  to  be  destroyed,  and  seeing  that  the  blocks  composing  the 
charge  are  in  intimate  contact,  the  detonator  is  placed  in  the  hole 
in  the  center  of  the  dry  primer  block  and  the  fuse  is  lit  or  the 
current  sent  through  the  wire,  as  the  case  may  be.  The  detona- 
tion of  the  dry  primer  will  set  up  detonation  in  all  the  blocks  and 
the  detonation  will  be  simultaneous  throughout  the  entire  mass. 
When  used  in  holes,  guncotton  should  be  dry,  as  wet  guncotton  is 
difficult  to  detonate  under  such  circumstances. 

424. — Detonators.  The  detonators  are  copper  tubes,  about 
3^  in.  in  diameter,  closed  at  one  end,  and  partially  filled  with  a 
fulminate  composition  which  is  ignited  either  by  a  fuse  or  by 
electricity.  The  ordinary  blasting  cap  (PI.  55,  Pig.  1),  or  detona- 
tor, is  intended  for  use  with  a  fuse,  and  is  designated  as  single, 
double,  or  triple  force,  according  to  the  amount  of  fulminate  com- 
position used.  In  all  military  work,  it  is  better  to  use  the  triple 
or  higher  force  caps,  as  their  action  is  sure,  even  on  comparatively 
low  explosives.* 

425. — The  fuse  generally  used  in  this  country  to  ignite  these 
detonators  or  caps  is  that  made  by  Ensign,  Bickford  &  Co.,  Sims- 
bury,  Conn.,  the  grade  known  as  "double  taped''  being  the  best  for 
general  work  when  the  fuse  is  not  exposed  to  prolonged  immer- 
sion in  water  or  damp  ground.  When  it  is  necessary  to  use  fuse 
for  submarine  explosives,  the  waterproof  fuse  should  be  used. 
The  rate  of  burning  of  the  fuse  should  be  found  by  experiment 
before  using.  This  is  done  by  taking  several  pieces,  1  ft.  long, 
and  finding  the  average  rate  of  burning  and  taking  this  as  the 
standard.  The  rate  at  which  this  fuse  is  intended  to  burn  is  3  ft. 
per  minute,  but  it  varies  somewhat,  so  that  when  great  nicety  is 
required  it  should  be  tested  as  above. 


*  Single  force  caps  contain  3  grs.,  double  force  caps  6  grs.,  and  triple  force  caps  9  grs. 
of  fulminate  of  mercury. 


"24.1  Demolitions. 

42G. — To  prepare  a  fuse  and  detonator  for  use,  cut  the  fuse  to 
the  length  required,  leaving  a  square  end ;  insert  this  end  in  the 
detonator  until  it  rests  against  the  fulminate,  taking  care  not  to 
scratch  the  fulminate.  Then  crimp  the  copper  against  the  fuse 
so  as  to  hold  it  firmly  :  this  is  done  by  means  of  pincers  made  for 
the  purpose ;  or,  in  case  these  are  not  available,  any  pincers  or 
the  edge  of  a  dull  knife  may  be  used,  being  careful  not  to  crimp 
on  the  portion  of  the  cap  containing  the  fulminate.  When  ready 
to  fire,  insert  the  detonator  in  the  hole  in  the  center  of  the  prim- 
ing block,  secure  it  by  tying  with  wire  or  twine,  and,  when  ready, 
light  the  fuse. 

To  ignite  powder,  the  fuse  alone  is  used,  being  placed  so  that 
the  end  is  well  centered  in  the  mass  of  the  powder  and  so  secured 
that  it  cannot  pull  out. 

427. — Electrical  fuses  and  detonators  are  constructed 
so  that  ignition  takes  place  upon  the  passage  of  a  current  of  suf- 
ficient intensity  through  a  platinum  wire,  around  which  is  wrapped 
some  fleecy  guncotton  or  other  inflammable  material  which  is  ignited 
by  the  platinum  wire  being  heated  to  redness  when  the  current  is 
turned  through  the  primer,  this  ignites  the  rest  of  the  composition 
which  causes  detonation  or  explosion  as  the  case  may  be. 

Two  forms  are  shown — the  commercial  (PI.  55,  Fig.  2)  and  the 
service  (PI.  57,  Fig.  10.)  The  commercial  is  so  constructed  that 
it  can  be  used  with  maximum  effect  only  in  detonating  compounds; 
while  the  service  fuse,  by  removal  of  the  copper  cap  containing 
the  fulminate,  is  converted  into  a  simple  electric  fuse  and  maybe 
used  to  ignite  gunpowder  mines.  The  current  of  electricity  is 
generated  by  means  of  a  battery  consisting  of  several  cells  or  by 
electrical  machines  of  various  forms.  The  means  now  generally 
used,  and  the  one  that  gives  surest  results,  is  the  magneto  ma- 
chine. On  account  of  its  portability  and  compactness,  and  be- 
cause of  its  simplicity,  the  *'Laflin  &  Rand  Exploder,  No.  3,"  is 
recommended  for  all  work  when  electricity  is  to  be  used  as  the 
igniting  agent.     (Fig.  3.) 

428.— When  more  than  5  fuses  are  to  be  fired  in  one  series,  it 
is  advisable  to  use  a  larger  machine  of  the  same  construction.  In 
favorable  cases,  the  machine  in  question  will  ignite  as  high  as  12 
charges,  but,  in  military  work,  it  is  best  to  leave  nothing  to 
chance,  and  the  limit  stated  above  is  a  good  one.  The  machine 
is  cased  in  wood  and  its  dimensions  are  13  x  8  x  5i  in.,  and 


PLATE  56. 


FIGl 


FIG  4. 


FIG,  6 


I 

I 

f    ■ 

-ll. 

tv 

v!s-sr3=3: 


Demolitions.  247 

weighs  18  lbs.  The  connecting  wires  are  attached  to  two  brass 
binding  posts,  which  are  found  on  the  top  of  the  box.  The  handle 
on  top  of  the  box  is  lifted,  withdrawing  the  ratchet  bar  to  its  full 
length,  and,  when  the  time  arrives  to  fire  the  charge,  the  bar  is 
pushed  vertically  downwards;  moving  slowly  for  the  first  inch  or 
two,  then  by  a  swift,  but  even  pressure  till  the  lower  end  is 
stopped  at  the  bottom  of  the  box. 

Ill  all  connection  of  wires,  at  least  2  in.  of  each  wire 
must  be  cleaned  bright  and  well  wrapped  around  one  another, 
as  shown  in  PI.  55,  Fig.  4 ;  under  no  circumstances  simply  hook 
wires  together. 

429. — After  wires  are  joined,  the  joint  should  be  insulated  by 
winding  rubber  tape,  or  wide  rubber  bands,  around  so  as  to  over- 
lap the  next  previous  turn.  When  water  has  to  be  encountered, 
wrap  with  rag  or  a  strip  of  linen  and  cover  with  tar  ;  or,  use  rub- 
ber tube  as  shown  :  the  tube  in  this  case  is  placed  on  one  of  the 
wires,  and,  when  the  joint  is  made,  is  pulled  over  it  and  tied 
tightly  to  the  wires  on  either  side  of  the  joint.     (PL  57,  Fig.  9.) 

Where  dynamite  is  used,  a  hole  is  made  for  the  detonator  in 
the  end  of  the  cartridge  with  a  sharp  stick  or  lead  pencil  and  the 
detonator  with  fuse  or  wire  attached  is  inserted ;  the  envelope  is 
then  tied  around  the  fuse,  so  that  the  detonator  cannot  become 
detached  from  the  cartridge,  care  being  taken  to  place  the  detona- 
tor in  cartridge  only  about  %  its  length,  so  that  the  charge  may 
not  be  ignited  by  sparks  from  the  fuse  before  the  detonator  is  ex- 
ploded, and  all  is  ready.  When  electricity  is  used,  push  the  deto- 
nator in  its  full  length  and  take  two  half  hitches,  with  wires,  about 
the  cartridge,  so  as  to  hold  every  thing  in  place.     (PI.  56,  Fig.  1.) 

In  all  cases,  where  more  than  one  package  or  piece  of  guncotton 
or  dynamite  is  used,  the  closest  contact  possible  should  be  made 
between  the  explosive  and  the  material  to  be  destroyed,  and  also 
between  the  different  pieces  of  explosive.  In  all  cases  wherever 
the  magneto  machine  is  to  be  used,  be  careful  not  to  connect  the 
wires  with  machine  till  every  one  is  at  a  safe  distance  from  the 
place  of  explosion.  When  more  than  one  charge  is  fired,  the 
wires  leading  to  the  several  charges  should  be  connected  as  shown 
in  PI.  57,  Fig.  6. 

430.— To  fell  trees,  bore  a  hole  at  the  height  desired,  in- 
sert the  charge,  and  Hre,  care  being  taken  that  the  center  of  the 
charge  is  about  the  center  of  the  tree.    If  the  charge  be  of  a 


218  iJKMof.i'noxs. 

length  equal  to  or  less  than  the  dianioter  of  the  tree,  then  the 
hole  may  be  bored  directly  through  ;  but  if  greater,  then  two  or 
three  holes,  intersecting  at  the  center,  must  be  bored. — Charge  in 
ounces  may  be  calculated  by  the  formula  c  =r  6d^,  in  which  c  is 
charge  in  ounces  and  d  the  diameter  in  feet.  To  make  the  tree 
fall  in  a  given  direction,  tie  a  rope  to  that  side  and  pull.  When 
time  is  not  available  to  bore  a  hole,  make  a  necklace  and  bind 
around  tree. — Charge  in  ounces  =  iSd"^.  When  impracticable  to 
make  necklace,  place  charge  in  a  bag,  or  support  by  stakes,  so 
that  all  the  explosive  is  against  one  side  of  tree,  and  fire. — Charge 
in  ounces  =  GOd^.  In  this  case,  the  tree  will  generally  fall 
towards  the  side  of  explosive.  This  method  of  felling  trees  is 
more  expensive  than  with  the  axe,  and  is  not  resorted  to  except 
when  time  is  not  available  for  the  slower  method.  It  is  not  ad- 
visable to  use  either  of  the  last  two  methods  when  it  can  be 
avoided,  as  there  is  great  waste  of  explosive.  (PL  55,  Figs.  5,  6,  7 
and  8.) 

431. — To  destroy  bri(lg:c  timbers,  if  rectangular,  the 
charge  is  placed  across  the  whole  width  of  the  beam;  10  ozs.  will 
destroy  a  beam  12"  high  and  6"  thick.  The  charges  for  other  di- 
mensions vary  with  the  height  and  square  of  the  thickness.  Charges 
may  be  calculated  by  the  formula  c=3  li  T  ^  in  which  c  equals 
the  charge  in  lbs.,  h  the  height,  and  T  equals  thickness  in  ft.  If 
the  timbers  are  circular  or  square,  the  charge  will  be  same  as  for 
trees,  taking  the  diameter  of  the  round  and  the  side  of  the  square 
one  as  d  in  the  formula  given.     (PL  56,  Pig.  2.) 

432.— When  high  explosives  are  not  on  hand,  the  bridge  tor- 
pedo used  in  the  war  of  the  rebellion  may  be  used.  It  consists  of 
a  bolt  8  or  9  in.  in  length,  surrounded  by  a  tin  cylinder  2  in.  in 
diameter  and  filled  with  powder.  The  ends  of  the  cylinder  are 
closed  by  iron  washers,  and  a  fuse  placed  in  one  end.  To  use  this 
torpedo,  a  hole  2|  in.  in  diameter  is  bored  in  the  timber  and  the 
torpedo  inserted  having  its  center  at  the  center  of  the  timber;  it 
is  then  exploded  by  means  of  a  fuse.  If  necessary,  two  may  be 
placed  in  holes  bored  at  right  angles  to  each  other.     (Fig.  4.) 

433.^Palisading  up  to  10  in.  in  thickness  takes  4  lbs.  of 
guncotton  for  each  ft.  in  length  to  be  destroyed. 

434. — For  stockades,  when  the  timbers  are  close  together — 
4  lbs.  of  guncotton  per  foot  in  length. 

If  the  timbers  are  squared,  the  blocks  of  cotton  may  be  fastened 


Demolitions.  241) 

to  a  thin  board  and  placed  against  the  foot  of  the  stockade,  but  if 
of  rough  logs,  tie  the  blocks  together  so  that  they  may  adapt 
themselves  to  the  form  of  the  timbers. 

When  stockades  are  double,  and  separated  by  a  distance  of  one 
yard  -25  lbs.  of  guncotton  per  foot  in  length  or  one  charge  of  80 
lbs.  may  be  placed. 

Railway  iron  stockades  are  breached  by  7  lbs.  per  foot  in 
length. 

In  all  cases,  distribute  the  charge  so  as  to  cover  the  length  de 
sired  to  be  breached. 

435. — To  cut  steel  rails,  use  one  block  of  guncotton, 
weight,  10  ozs.,  tie  the  block  against  the  web  of  the  rail  with  wire 
or  twine,  and,  if  possible,  tamp  well  with  earthy  and  explode. 
(Fig.  3.) 

To  blow  a  piece  of  some  length  out  of  a  rail,  arrange  two 
charges  of  10  oz.  as  shown  above,  placing  one  on  each  side  of  the 
rail  at  a  distance  apart  of  5  or  6  ft.;  these  should  be  exploded 
by  use  of  a  magneto  machine  so  that  the  action  may  be  simul- 
taneous in  both  charges;  the  section  will  be  blown  out  and 
turned  on  its  center,  making  a  large  opening.     (Fig.  5.) 

436.— Switch  points  maybe  destroyed  by  lodging  a  block 
of  cotton  between  the  outer  rail  and  the  pivot  end  of  the  switch 
point,  being  careful  to  tamp  as  completely  as  possible,  ("A"  PL 
51,  Fig.  11.)  In  the  case  of  frogs,  one  10  oz.  block,  placed  in  the 
angle  of  the  frog,  will  destroy  the  point  and  render  it  useless. 
(^'A/'Pl.  52,  Fig,  1.) 

437.  To  destroy  a  wooden  truss  bridge,  blow  away 
the  main  brace  of  the  panel  nearest  to  an  abutment  or  pier;  it  is 
really  necessary  to  blow  only  one  side  down  but  it  is  better  to  be 
sure  and  destroy  both  sides.  If  the  bridge  has  an  arch  of  wood 
besides  the  truss  then  destroy  the  arch  on  each  side.  If  time  is 
available,  the  bridge  may  be  burned;  to  do  this,  collect  brush, 
etc.,  and,  if  possible,  place  it  under  one  end  so  as  to  burn  it  oif 
and  cause  the  span  to  drop,  but  if  not  possible,  build  the  fire  in 
the  center  of  the  span;  it  will  burn  through  and  cause  rupture  in 
the  center. 

In  all  cases  attack  span  over  the  deepest  water. 

438. — To  cut  wrouglit  iron  plates  the  charge  of  gun- 
cotton  in  pounds  is  found  from  the  formula  c  =1.5wt2  in  which 
c  equals  charge,  w  the  width  of  plate  to  be  cut  in  feet  and  t  the 


250  Demolitions. 

thickness  in  inches.    The  charge  must  be  placed  entirely  across 
the  plate  to  be  cut. 

439.— To  calculate  the  charge  necessary  to  rupture  an  iron, 
bridge  beam  or  girder,  calculate  the  charge  for  each  separate  cross 
section  to  be  cut  and  add  the  results;  the  sum  will  be  the  charge 
required.  The  charge  is  most  conveniently  placed  on  the  side  of 
the  beam,  reaching  entirely  across  and  bound  on  with  wire,  the 
I^rimer  being  in  the  center  of  the  charge.  If  possible,  a  board 
should  be  tied  over  the  whole  charge  and  earth  tamped  in  around 
it.  When  time  is  not  available  for  the  placing  of  the  charge  as 
descrihoil  above,  then  it  may  be  placed  on  top  of  the  beam  or  on 
the  liange,  the  charge  being  calculated  by  the  above  formula.  In 
demolishing  iron  girder  bridges  the  charge  is  applied  as  described 
for  iron  girders.  (Figs.  6  and  7.)  When  the  girder  bridges  are  only 
short  ones  up  to  20  ft.  in  length,  they  may  be  overturned  by  levers 
and  thrown  down  from  the  abutment. 

440.  When  it  is  necessary  to  destroy  truss  bridges  the  most 
lavoiahlr  place  for  the  charge  is  at  the  center  of  the  span  on  the 
lo\v(u-  cliord.  When  the  bridge  is  of  the  variety  known  as  a  deck 
bi-idgc.  the  charge  should  be  jjlaccd  on  the  top  member,  the 
amount  necessary  being  calculated  as  shown  above.  When  the 
lower  or  tension  member  is  composed  of  eye  bars  the  charge 
should  be  placed  between  alternate  pairs  of  eye  bars  as  near  to 
the  coupling  pin  as  possible.  (PI.  57,  Fig.  1.)  When  bridges  are 
supported  by  iron  or  wood  piers,  it  is  sometimes  possible  to  des- 
troy the  piers  and  thus  bring  down  the  entire  structure.  The 
charges  may  be  calculated  by  formulas  for  iron  or  wood  as  the 
case  may  be.  It  is  best  to  destroy  the  supports  on  both  sides  of 
the  pier  as  this  will  infallibly  bring  down  the  entire  structure. 

441 .  1 11  (lestroyiiig  siisi)eiisic>ii  ll)ri(lges,  blow  down  the 
towers  below  the  saddle,  excavate  and  blow  out  one  of  the  anchor- 
ages or  cut  the  cable  with  guncotton.  The  charge  for  bridge 
cables  is  calculated  as  for  cutting  iron  plates,  but  the  charge  must 
be  very  carefully  placed  so  as  to  be  in  close  contact  with  the  cable. 
If  the  cables  are  made  of  plates,  the  plates  may  be  cut  tcith 
cotton,  as  in  the  case  of  eye  bars,  cited  above.  Where  bridges  of 
iron  or  wood  are  supported  by  masonry  piers,  the  piers  may  be  de- 
stroyed by  charges  calculated  by  the  formulas  given  below. 

442." To  blow  down  a  Avail,  the  charge  should  be  placed 
against  the  bottom  as  close  to  the  wall  as  possible,  and  if  possible, 


PLATE  57. 


Demolitions.  253 

should  be  tamped.    If  time  allows,  a  channel  should  be  cut  in  the         ^ 
wall  at  the  seat  of  the  charge.    When  untamped,  c  =^^t2  where  c        /^ 
equals  charge  in  pounds,  w  width  of  wall  to  be  breached,  and  t 
thickness,  w  and  t  being  in  feet;  and  when  tamped  with  earth  equal 
in  thickness  to  the  wall,  half  the  above  charge  may  be  used. 
(Pig.  2.) 

44:3. — Bridge  piers  in  masonry  may  be  destroyed  by  charge  of 
I  Wt^  poll  running  foot.  This  means  excessive  expenditure  of  ex- 
plosive and  would  not  be  used  against  short,  thick  piers.  In  case 
one  has  to  be  destroyed,  place  small  charges  in  chambers  exca- 
vated as  deep  as  possible  in  the  masonry,  and  explode  all  simul- 
taneously; calculate  charges  as  for  walls.  Masonry  bridges 
should  be  attacked  at  the  haunches;  if  that  is  not  possible,  then 
blow  in  the  crown.  When  attacking  the  crown,  place  explosive 
in  trenches  clear  across  the  bridge,  and,  if  possible,  on  the  ma- 
sonry of  the  arch  itself;  better  use  two  trenches,  each  placed, 
from  the  middle  of  the  bridge,  a  distance  equal  to  |  the  width  to 
be  breached  at  the  crown  or  arch;  calculate  charge  for  each 
trench  clear  across  the  roadway.  If  haunches  are  attacked,  dig 
down  as  far  as  desired  and  place  charge  clear  across  on  back  of 
masonry;  charge  f  Wt^  if  untamped,  and  half  of  this  if  tamped. 
(Fig.  3.) 

444. — Gates  may  be  blown  in  with  50  lbs.  of  guncotton  ex- 
ploded in  one  charge.  The  charge  is  hung  against  the  center  of 
gate  by  means  of  a  sharpened  pick  or  on  a  nail.  This  charge  is 
large,  but  gates  will  generally  be  strengthened  in  some  man- 
ner on  the  inside.     (Fig.  4.) 

445. — Houses  may  be  blown  down  or  shattered  by  placing 
charges  in  the  center  of  the  floor  and  closing  all  outlets  such  as 
doors,  windows,  etc.  Charge  according  to  the  size,  20  lbs.  being 
sufficient  for  small  houses. 

446. — Tunnels  may  be  destroyed  by  placing  charges  back  of 
the  masonry  at  the  spring  of  the  arch.  If  possible  the  charge 
should  be  placed  in  a  chamber  excavated  behind  the  arch  and 
well  tamped.  Tunnels  should  be  blow^n  in  at  several  places,  so 
as  to  render  it  impossible  to  repair  them  in  a  short  time.  Charges 
as  for  bridge  arches.     (Fig.  8.) 

447. — One  and  one-half  pounds  guncotton  detonated  on  the 
chase  will  disable  field  or  siege  guns;  the  damage  is  more  consid- 
erable when  the  charge  is  tamped.    If  not  damaged  by  the  first 


^ 


254  Demolitions. 

explosion,  double  the  charge  and  explode  in  the  same  place. 
Heavy  fortress  guns  may  be  disabled  by  destroying  their  car- 
riages by  the  use  of  guncotton.  Wherever  gunpowder  is  used  as 
an  explosive  it  should  be  enclosed  in  stout  bags,  preferably  two, 
and  the  outer  one  well  tarred.  This  is  to  protect  from  accidental 
explosion  set  up  by  sparks  from  the  fuse.    (Fig.  5.) 

448. — The  following  table  gives  in  a  concise  form  all  informa- 
tion necessary  for  the  use  of  guncotton  and  gunpowder.  The 
table  shows  approximately  the  value  of  the  different  high 
explosives  as  compared  with  guncotton. 

Note: — Charges  are  in  lbs.;  B  and  T  are  in  feet ;  t  is  in  inches. 

B  is  length  of  breach  to  be  made ;  T  or  t  is  thickness  of  object 
to  be  demolished. 

Gunpowder  is  assumed  to  be  roughly  tamped  with  sand-bags. 
Guncotton  is  untamped.  If  the  guncotton  is  tamped,  the  charges 
may  be  reduced  by  about  one-half. 

Charge  of  guncotton  must  be  equal  in  length  to  the  breach 
which  is  to  be  made. 


Hasty  Demolitions. 


255 


Object  attacked 

Gunpowder 

Guncotton 

Remarks 

Brick  arch "^ 

r 

|BT2 

2  lbs.  per 

The    length    of 
breach,  B,  should 

Brick  wall,  2  ft.  or 

less 

Brick  wall  over  2  ft. 

thick 

Brick  piers ^ 

|BT2   < 

foot  run 

|BT2 
|BT2 

^not  be  less  than  the 
height  of  the  wall 
to  be  brought  down. 

Hard  wood  (e.  g.,  teak, 

40  to    100 

^Lm^ 

In  a    concentrated 

oak,    elm),    in    any 

lbs.   for 

-b^rr"^ 

charge,  or  for   trees 

form,     whether 

stockade 

not  over  12  in.  diame- 

stockade,   palisade, 

ter,  in  a  necklace. 

single    timbers. 

^nr^ 

In  auger  hole,  when 

trees,  etc 

the  timber  is  not  per- 
fectly round,  T  =  the 

Soft  wood 

Half  the 
for  hard 

charges 
wood 

smaller  axis. 

Breastwork    of    hori- 

60 to   80 

4  lbs.  per 

zontal     balks,    or 

lbs.    per 

foot 

earth,    between 

5  ft. 

sleepers,  up  to  3  ft. 

6  in.  thick 

7  lbs.  per 

Heavy  rail  stockade . . 

foot 

Fortress  gate 

200  lbs. 

50  lbs. 

Iron  plate 

1  Bt2 

In  this  case  only,  t 
is  in  inches. 

2 

Field  or  Siege  guns. . 

\\  lbs. 

On  chase  near  muz- 
zle. 

Heavier  guns 

4  lbs. 

In  bottom  of  bore, 
tamped  with  water  or 

sand. 

First-class  iron  rail.. . 

1  lbs. 

Touching    web    of 
rail  and  near  a  chair. 

"        "     steel  rail . . 

4  ozs. 

Four  rails   placed 
round  the  charge  will 
be  cut  simultaneously 
by  it. 

25G  Demolitions. 

Approximate  Relative  Strength  of  Some  op  the  High 
Explosives. 

Exijlosive  gelatine 128.3 

Nitroglycerine 120.3 

Guncotton 100 

Dynamite,  No.  1,%%  Nitro  glycciino 07.8 

Rack-a-Rock 74.2 

Dynamite,  50% 72.7 

449.— Destruction  of  Obstacles.      Wire  entanglements 

may  be  destroyed  by  cutting  with  wire  nippers,  or,  if  they  are  not 
at  hand,  then  the  ordinary  hand  axe  will  do,  taking  care  to  cut 
against  the  picket. 

450. — Abatis  is  very  difficult  to  destroy  and  cannot  be  re- 
moved while  fire  can  be  brought  to  bear  on  the  spot.  Pry  up  the 
pickets  with  levers  and  attach  ropes  to  the  butts  of  trees  and 
haul  away. 

451. — Palisades  and  stockades  are  cut  away  with  axes  or 
saws,  the  cuts  being  made  near  the  bottom  and  ropes  being  at- 
tached to  the  tops  of  the  timbers;  or  dig  out  the  earth  at  the  bot- 
tom and  pull  them  over. 

452.— Small  pickets  are  cut  through  with  the  axe,  or,  if 
possible,  pulled  up. 

453.— Small  pits  are  filled  with  earth,  brush,  or  covered 
by  planks,  fascines,  or  bales  of  hay. 

454. — Automatic  torpedoes  are  easily  destroyed  by  driv- 
ing animals  up  and  down  the  line  suspected  of  containing  them. 


ClIAPTEIl   XXT.— Camping  Expedients. 


455. — There  are  a  few  general  principles  which  should  be  ob- 
served in  selecting  a  camp,  whether  the  troops  are  to  be  estab- 
lished in  bivouac,  in  tents  or  in  huts.  These  principles  relate  to 
the  health  and  comfort  of  the  troops,  the  facilities  for  communi- 
cation, the  conveniences  of  wood  and  water,  and  the  resources  of 
the  locality  in  provisions  and  forage. 

450. — For  an  intrenched  camp  the  ground  must  be  selected 
with  particular  reference  to  its  adaptability  for  defense  and  the 
oamj)  arranged  with  that  object  in  view,  at  the  same  time  observ- 
ing as  many  of  the  other  requirements  as  possible. 

457. — Dry  and  liealtliy  sites,  dependent  on  soil: 
Granite,  metamorpliic  and  trap  rocks,  usually ;  clay  slates,  but 
drinking  water  is  scarce;  limestone  generally,  but  the  water  is 
hard,  clear  and  sparkling  though  sometimes  contaminated;  deep 
permeable  sandstones,  if  the  air  and  soil  are  dry ;  deep  gravels, 
unless  lower  than  surrounding  country  ;  pure  sand,  deep  and  free 
from  organic  matter  ;  icell  cultivated  soils  generally ;  gravelly 
hillocks,  the  very  best. 

458.— ^Unliealtliy  sites,  dependent  on  soil:  Magnesium 
limestone;  shallow  sandstone  underlaid  with  clay;  clay  and 
alluvial  soils  generally ;  rice  fields ;  made  soils  usually  ;  newly 
plowed  ground. 

459.— Healthy  sites,  independent  of  soil:  The  best  is 
on  a  divide  or  saddle,  unless  too  much  exposed  or  without  water. 
The  next  best  is  near  the  top  of  a  slope  and  the  southern  side  is 
preferable  to  the  northern;  banks  of  running  rivers  are  good, 
if  not  marshy. 

460.— Unliealtliy  sites,  independent  of  soil:  Enclosed 
valleys,  ravines,  or  the  mouths  of  long  ravines,  ill-drained 
ground,  the  neighborhood  of  marshes,  especially  if  the  wind 


258  Camping  Expedients. 

blows  from  them.  If  forced  to  camp  near  a  marsh  the  windward 
side  should  be  selected  and,  if  possible,  have  a  hill  or  a  screen  of 
woods  or  brush  between  the  camp  and  marsh.  Moss  generally 
indicates  marshy  ground. 

461. — Sites  affected  by  siirroiiiidiiig  vegetation: 
Herbage,  or  closely  lying  grass,  is  always  healthy,  but  should  be 
kept  cut  and  all  weeds  destroyed ;  heavy  brush  about  a  marsh 
should  not  be  removed.  Trees,  in  cold  countries,  break  the  winds; 
in  hot  countries,  they  cool  the  ground  and  may  protect  against 
malarial  currents  ;  so  should  only  be  removed  with  judgment. 

462.— In  selecting  camps,  wood,  water  and  grass  should 
be  secured  if  possible,  together  with  good  drainage,  but  marshy 
ground  should  not  be  occupied  even  for  a  night. 

Old  camp  grounds  sliould  never  be  occupied  if  avoid- 
able; instead,  go  as  far  as  possible  to  the  windward  side  of 
them. 

The  site  having  been  selected,  the  details  of  castrametation,  or 
the  laying  out  of  camps  for  the  different  arms  will  be  found  in 
the  authorized  Drill  Regulations  of  each. 

463. — Water  is  more  immediately  necessary  to  life  than 
food. 

Each  man  requires  on  the  march  for  drinking  and  cooking  8  to  4: 
quarts  per  day,  and  an  equal  amount  for  washing.  In  stationary 
camps  5  gallons  per  da}^  for  all  purposes. 

Hospitals  require  several  times  as  much  per  man  per  day. 
Horses,  mules  and  cattle  require  from  6  to  10  gallons  each  per 
day  for  drinking.     It  should  be  soft  and  clean,  if  possible. 
Sheep  and  hogs  require  from  2  to  4  quarts  each,  per  day. 
464. — It  is  iinperative,  on  going  into  camp,  that  the  supply 
he  immediately  looked  aftei^  and  a  guard  placed  over  it.    If  the 
supply  be  small,  si^ecial  precautions  must  be  taken  and  an  officer 
put  in  charge. 

465. — Good  drinking  Avater  should  be  bright,  colorless, 
odorless,  free  from  sediment,  of  pleasant  and  sparkling  taste. 

Rain  water,  collected  from  a  clean  surface,  after  the  atmos- 
phere has  been  well  washed,  is  the  purest  in  nature.  Sp>rings 
whose  origins  are  remote  from  habitations,  streams  flowing 
through  uninhabited  regions,  and  large  lakes,  furnish  the  next 
best  sources  of  supply. 


Camping  Expedients.  259 

466. — If  the  supply  he  from  a  lake,  pond,  or  stream,  separate 
places  for  obtaining  water  for  men  and  animals  must  be  marked 
out,  and  care  taken  that  the  margin  is  not  trampled  into  mud  and 
the  water  made  turbid.  Where  this  is  likely  to  occur  when  ani- 
mals are  watered  direct  from  the  source  of  supply,  a  hard  bottom 
should  be  formed  for  them  to  stand  on,  and  a  barrier  formed  to 
prevent  them  going  out  too  far. 

It  is  better,  when  convenient,  to  arrange  rows  of  sunken  half 
barrels,  or  board  troughs  raised  above  the  ground,  into  which  the 
water  can  be  drawn.  If  the  supply  be  limited,  it  may  be  necessary 
to  connect  the  troughs  to  prevent  waste;  if  not  limited,  each 
should  be  supplied  direct  from  the  source  and  the  overflow 
drained  off.  Even  when  drinking  from  a  running  stream,  the  ani- 
mals below  get  foul  water.  To  prevent  the  ground  around  the 
troughs  becoming  muddy  it  should  be  paved  and  drained  along 
the  whole  length  and  for  a  distance  of  10  or  12  ft.  back.  Where 
troughs  cannot  be  constructed,  trenches  lined  with  puddled  clay 
may  be  made  to  answer. 

Arrangements  should  be  made  so  animals  may  be  brought  up 
from  one  direction  and  leave  in  another  without  confusion  or 
crowding.  ^ 

467. — If  the  supply  he  from  a  stream,  the  water  for  drinking 
and  cooking  for  the  troops  is  drawn  highest  up;  for  the  animals  to 
drink,  next  below;  and  for  washing,  bathing,  etc.,  lowest  down; 
while  all  drainage  should  enter  below  where  any  water  is 
taken. 

If  the  stream  be  small  it  may  be  necessary  to  construct  a  series 
of  small  reservoirs  by  building  small  dams  across.  Animals 
drink  better  and  more  rapidly  where  water  is  5  or  6  in.  deep. 

468. — If  unavoidable,  water  from  small  ponds  and  shallow 
wells  should  only  be  used  after  being  boiled  half  an  hour,  then 
aerated  and  filtered. 

4:69,— If  the  supply  he  from  springs,  each  should  be  enlarged 
and  surrounded  by  a  low  puddled  wall,  to  keep  out  surface 
drainage.  They  may  be  lined  with  casks  or  barrels  charred  in- 
side, or  gabions,  afterwards  working  in  puddled  clay  between  the 
earth  and  linings.  The  overflow  may  be  received  into  a  succes 
sion  of  casks  let  into  the  ground  close  together. 

Surface  springs  should  be  sought  for  in  hollows,  at  the  foot  of 


200  CAMl'lMi    Exi'KDlKiN'J'S. 

hills,  where  the  earth  is  moist,  the  grass  unusually  green,  or  the 
thickest  mists  arise  mornings  and  evenings. 

470. — If  water  is  not  immediately  available  it  may  be  neces- 
sary to  dig  wells.  The  most  expeditious  means  of  doing  so  is  to 
use  Well  Augers.     (PI.  58,  Figs.  1,  2  and  3.) 

47 1  .—To  dig  a  well, an  auger  is  attached  to  a  rod  sus  jjended 
from  a  rope  passing  over  a  pulley  at  the  top  of  a  derrick  or  tripod 
and  thence  to  a  windlass.  To  the  auger  rod  is  secured  an  arm  or 
arms  by  which  the  auger  is  turned  by  hand  and  so  screwed  down 
into  the  earth.  About  eight  turns  fills  the  auger,  which  is  then 
lifted,  emptied  and  replaced. 

472. — The  auger  for  boring  in  quicksaiid  (Fig.  3)  is  shaped 
similarly  to  the  ordinary  wood-boring  auger,  but  with  a  hollow 
shank,  so  that,  when  lifted,  no  suction  is  produced.  When  the 
thread  becomes  loaded  the  auger  is  drawn  up  into  an  enclosing 
cylinder,  removed  from  well  and  emptied. 

473. — Driven  Avells.  The  driven  tube-well  consists  of  a  tube 
about  3  ft.  long,  perforated  with  holes,  and  furnished  with  a  steel 
point  of  bulbous  form  (Fig.  4)  and  as  many  other  plain  iron  tubes 
as  may  be  necessary. 

The  form  of  the  point  serves  to  clear  a  passage  for  the  sockets 
by  which  the  tuSes  are  screwed  together. 

474. — To  drive  a  Avell,  a  tube  is  screwed  to  the  point  (Fig. 
5)  and  on  this  a  clamp  is  fastened  by  two  bolts  at  about  3  ft.  from 
the  lower  extremity  of  the  point.  Next,  an  iron  driving  weight, 
or  monkey,  is  slipped  on  the  tube  above  the  clamp.  The  tube  thus 
furnished  is  raised  and  held  vertically  in  the  center  of  a  guide  in 
w^hich  it  is  retained  by  a  latch.  The  whole  being  now  arranged 
in  position,  ropes  are  made  fast  to  the  monkey  and  passed  over 
pulleys  on  the  guide,  and  driving  commenced  by  two  men  pulling 
the  ropes  and  allowing  the  monkey  to  fall  on  the  clamp.  As  soon 
as  the  clamp  reaches  the  ground,  the  monkey  is  raised  and  held  up, 
the  clamp  loosened  and  raised  1.5  or  2  ft.,  tightened,  and  the  driv- 
ing continued  as  before  until  the  top  of  the  tube  comes  below  the 
hole  in  the  top  of  the  guide  head,  when  the  lengthening  bar, 
(Fig.  7)  is  dropped  into  the  top  of  the  well-tube.  The  lengthen- 
ing bar  consists  of  a  length  of  the  well-tubing  with  a  smaller  pipe 
brazed  into  one  end  and  projecting  about  1  ft.,  which  tits  into  the 
well-tube.  This  bar  keeps  the  tube  steady  and  serves  as  a  guide 
for  the  monkey  to  slide  on  until  the  top  of  the  well-tube  reaches 


PLATE  58. 


Fig.l3. 


Camping  Expedients.  263 

to  within  a  foot  of  the  ground.  The  lengthening  bar  is  then  re- 
moved, another  tube  is  screwed  on,  and  the  driving  continued 
until  water  is  reached.  A  hollow  iron  plumb  is  frequently 
lowered  into  the  tube  to  ascertain  when  water  has  been  reached 
or  whether  earth  of  any  kind  has  got  into  it. 

Accumulations  in  the  tube,  of  a  loose  sandy  nature,  can  be 
pumped  up,  by  screwing  a  funnel  (Fig.  8)  on  top  of  the  tube, 
then  lowering  into  it  through  the  funnel  a  smaller  tube  with  a 
pump  attached.  Water  poured  into  the  funnel  runs  down  out- 
side the  smaller  tube  and  is  pumped  up  through  it  bringing  the 
mud  and  sand.  When  water  is  struck,  and  stands  several  feet  in 
the  tube,  the  pump  is  screwed  on  to  the  well  tube. 

The  well  can  also  be  driven  without  the  use  of  the  tripod  sup- 
ports (Fig.  6)  care  being  taken  to  keep  the  tube  vertical  by  means 
of  guy  ropes.  Such  a  well  can  be  driven  from  10  to  20  ft.  per 
hour.  The  tubes  can  be  withdrawn  without  damage  by  reversing 
the  operations  of  driving.     (Fig.  9.) 

475. — ^The  tube-well  is  not  intended  for  piercing  rock,  or  solid 
stone  formations,  but  is  quite  capable  of  penetrating  very  hard 
and  compact  soils.  When  striking  rock,  stone,  or  deep  beds  of 
clay,  it  is  best  to  pull  up  the  tube  and  try  in  another  spot,  for  by 
going  a  little  distance  ojff  water  will  in  many  cases  be  found. 

476. — Clariflcation  of  Abater.  Water  usually  contains 
mineral  and  organic  substances  in  solution  and  in  suspension. 
Substances  in  solution  completely  disappear  and  cannot  be  en- 
tirely filtered  out.  Substances  in  suspension  do  not  entirely  dis- 
appear and  may  be  filtered  out. 

477. — Hard  water  contains  one  or  more  substances,  as  lime, 
magnesia,  iron  and  others,  in  solution,  which  are  liable  to  pro- 
duce intestinal  troubles  to  persons  unaccustomed  to  them. 
Cooking  vegetables  in  it  is  very  difficult.  Washing  with  it  re- 
quires a  great  deal  of  soap. 

The  hardness  of  water  may  be  partially  removed  by  boiling  for 
half  an  hour  or  so,  or  by  adding  a  small  quantity  of  washing 
soda,  or  by  adding  a  couple  of  ounces  of  quicklime  to  100  gals. 

478. — Substances  in  suspension  may  be  largely  removed  by 
precipitation  and  filtration. 

479. — Precipitation  is  allowing  such  matter  as  will  to  settle 
through  its  greater  specific  gravity,  or,  by  inducing  it  to  do  so 
through  some  harmless  chemical   or    mechanical  action.      For 


liOl  CaMIMXC;    iilxi'EDlET^TS. 

which  purpose  nuiy  be  used  about  6  grains  of  crystallized  alum  to 
the  gallon,  or  tannin  in  small  quantities  and  letting  stand  several 
hours  before  using;  bruised  cactus  leaves,  also  tea  leaves  that 
have  been  used  act  similarly;  citric  acid,  1  oz.  to  16  gal.,  or  borax 
and  alum,  i^  oz.  each,  or  1  to  2  tablespoonfuls  of  ground  mustard 
to  a  barrel  improves  water. 

4S().  FiKratioii  is  iiiccluinicnlly  arresting  and  atlfact ini;- 
susjjended  matter,  and  removing  dissolved  matter  in  the  water. 
Filtering  materials  act  only  for  a  short  period  and  should  be  fre- 
quently cleaned. 

481. — Materials  icliich  may  he  used  are  sponge,  wool,  and  like 
articles  for  straining,  but  must  be  constantly  removed  and 
cleaned.  Clean  sand,  gravel,  and  porous  stone  remove  suspended 
matter,  but  have  little  or  no  effect  on  dissolved  organic  matter. 
Iron  sponge,  a  compound  of  sawdust  and  iron  oxide  heated  in  a 
furnace,  and  Carferal,  a  compositi(m  of  charcoal,  iron  and  clay, 
are  efficient  for  removing  mineral  matter.  Bone  black  or  animal 
charcoal,  and  wood  charcoal,  when  freshly  burned,  absorb  mineral 
Hiattcr  for  a  couple  of  weeks,  but  their  chief  action  is  on  organic 
matter. 

482.— Cliarcoal  may  be  made  by  digging  in  the  ground  a 
circular  pit,  some  6  in.  deep  by  4  or  5  ft.  across,  then  placing  a 
large  pole  or  bundle  of  brushwood  vertically  in  the  center. 
Around  this  the  wood  to  be  burned  is  piled,  forming  a  kind  of 
cone.  The  pile  is  then  covered  with  brush,  and  on  this  a  layer  of 
4  or  5  in.  of  earth.  (Fig.  10.)  The  center  pole  is  then  removed 
and  a  fire  lighted  in  its  place,  receiving  air  from  vents  left  at  the 
bottom  for  that  ijvirpose.  The  fire  proceeds  from  the  center  out- 
wards, and,  if  burning  properly,  the  smoke  is  thick  and  white.  If 
it  does  not  spread  to  every  part  new  vents  must  be  made.  If  the 
smoke  becomes  thin  and  a  blue  flame  appears,  it  is  burning  too 
fast,  and  vents  must  be  stopped  up  or  more  earth  thrown  on. 
When  the  smoke  ceases  to  escape,  the  vents  and  chimney  are 
closed  and  the  pile  allowed  to  stand  for  a  couple  of  days  until  it 
cools. 

From  20%  to  25%  of  charcoal  is  thus  obtained. 

483.— A  coiiveiiieiit  portable  Alter  (Fig.  11)  is  made 
by  taking  a  small  cylinder  of  compressed  carbon  and  inserting  it 
in  a  rubber  tube  in  such  a  manner  that  the  carbon  end  may  be 


Camping  Expedients.  2G5 

immersed  in  the  water,  then  applying  the  mouth  to  a  mouthpiece 
at  the  other  end  of  the  tube,  and  drawing  the  water  through. 

484. — Tlie  Success  Filter,  (Fig.  12)  consists  of  a  cylindrical 
I^orous  stone  4  in.  long  by  4  in.  in  diameter  with  a  hole  bored  in 
one  end.  In  this  hole  is  fitted  a  rubber  gasket  through  which 
passes  an  iron  tube  that  is  fastened  into  the  bottom  of  a  barrel, 
jar  or  bucket.  The  water  filters  through  the  stone  into  the  hole 
inside  and  passes  out  through  the  tube  into  a  receiving  vessel 
below.     (Fig.  13.) 

By  fastening  the  iron*  tube  into  the  bottom  of  a  large  empty 
tomato  or  peach  can,  in  which  the  stone  is  placed  on  the  tube  and 
wedged  fast,  then  fastening  a  rubber  tube  2  or  3  ft.  long  on  the 
iron  tube  outside  of  the  can,  a  syphon  filter  is  obtained.  The 
action  is  set  up  by  exhausting  the  air  from  the  stone,  after  the 
can  and  stone  are  immersed  in  water,  by  sucking  on  the  end  of 
the  rubber  tube  until  the  water  is  started. 

485.— A  simiile  water  filter  may  be  made  by  stuffing  a 
piece  of  sponge  in  a  hole  in  the  bottom  of  a  cask,  flower  pot,  or 
other  vessel,  (Fig.  14)  then  placing  above  this  a  layer  of  coarse 
sand,  then  a  layer  of  pounded  charcoal,  3  or  4  in.  thick,  then  an- 
other layer  of  coarse  sand,  and  on  this  a  layer  of  coarse  gravel. 
The  layers  should  be  thick  as  possible,  and  tightly  compressed, 
and  washed  thoroughly  clean  before  being  used.  The  different 
layers  may  be  prevented  from  mixing  by  perforated  boards,  or 
otherwise.     Another  form  may  be  made  as  shown  in  Fig.  15. 

486. — Casks,  or  barrels,  charred  on  the  inside  (and  occasion- 
ally cleaned,  brushed,  and  recharred)  improves  water. 

487.— I^atriiies.  Arriving  on  the  site  of  a  camp,  one  of 'the 
first  duties  is  to  designate  the  places  to  attend  to  the  calls  of  na- 
ture, and  there  dig  latrines.  Urinals  should  be  placed  nearer  the 
camp  and  of  easy  access. 

The  only  exception  to  digging  latrines  is  when  the  command  is 
very  small,  is  certain  to  march  the  next  day,  and  no  other  troops 
are  to  follow. 

488. — Latrines  and  urinals  should  be  so  placed  as  not  to  be  in 
the  course  of  the  prevailing  winds  to  the  camp,  and  must  be  so 
situated  that  they  cannot  pollute  the  water,  either  directly  or  by 


489. — A  small,  shallow  trench  will  suffice  for  a  single  night, 
and  should  invariably  be  filled  in  the  morning  before  marching. 


2GG  Campin(s  Expedients. 

For  longer  i)erio(ls,  a  trench  2  or  3  ft.  wide  at  top,  from  2  to  10 
ft.  deep,  and  12  to  15  ft.  long  for  every  100  men,  should  be  dug, 
throwing  the  earth  to  the  rear,  from  which  a  layer  of  a  few  inches 
should  be  thrown  into  the  trench  every  day,  or  oftener  if  neces- 
sary.    Lime  or  charcoal  may  also  be  used  to  deodorize  the  soil. 

It  is  better  to  increase  the  number  of  trenches  than  to  make 
;iny  one  trciu-h  too  long. 

Shallow  hitrines  should  be  discarded  when  tilled  within  a  foot 
of  the  surface,  and  completely  tilled  in  with  earth;  deep  ones 
when  within  3  or  4  ft.  of  the  surface. 

All  latrines  should  be  filled  in  and  marked  before  marching. 

490. — In  temporary  camps,  latrines  may  be  provided  with  seats 
of  a  pole  and  a  back,  and  be  screened  by  bushes,  canvas,  or 
other  means.    (Pig.  'iO.) 

491. — Kitclieiis.  On  going  into  camp,  kitchens  should  be 
promptly  established  and  in  the  same  relative  positions  as  if  the 
camp  were  going  to  last  a  month  or  more.  A  pit  should  be  dug 
near  by  for  strictly  liquid  refuse,  w^hile  solid  matter  should  be 
placed  in  a  l)()x  or  barrel  for  the  ])oliee  party  to  remove. 

492.  Wlioi  fuel  is  plentiful,  a  trench  of  sufficient  length  and 
about  1  ft.  deep  may  be  dug  to  contain  the  fire  over  which  the 
kettles  are  hung  from  supports.     (PI.  59,  Fig.  1.) 

If  fuel  is  scarce,  then  dig  a  trench  as  above  in  the  direction  of 
the  wind  but  a  little  narrow^er  than  the  diameter  of  the  kettles  to 
be  used.  Place  the  kettles  over  the  trench  and  fill  in  between 
with  stones,  clay,  etc.,  forming  a  kind  of  flue.  The  draft  may  be 
increased  by  building  a  chimney  of  sods,  stones,  etc.,  on  the  lee- 
ward end  and  enlarging  the  windward  end.     (Fig.  2.) 

If  the  camp  is  to  be  for  a  long  time  and  the  direction  of  the 
wind  liable  to  vary,  a  number  of  such  trenches  may  be  dug  radi- 
ating from  a  common  point,  over  w^hich  point  a  chimney  is  con- 
structed. Then,  whatever  the  direction  of  the  wind,  the  trench 
opening  in  that  direction  can  be  used,  the  others  being 
closed. 

The  trenches  should  have  a  slight  fall  from  the  chimney  back 
for  drainage,  and  a  means  for  the  water  to  escape.  If  the  kettles 
are  small  or  of  various  sizes,  rests  of  stones,  scraps  of  iron,  etc., 
may  be  placed  across  the  trench. 

A  square  hole  may  be  dug  for  the  fire  with  trenches  lor  draught 


PLATE  59, 


Camping  Expedients.  269 

at  the  corners,   the   kettles  being  placed  on  rests  over   the  fire. 
(Fig.  3.) 

4:93.-- A  grillage  ov  Jcind  of  grate  about  1  ft.  high,  made  of 
gas-pipe  or  bar-ironjis  sometimes  used  to  set  over  the  fire,  and  on 
this  are  placed  the  kettles.  (Fig.  4.)  These  are  sometimes  made, 
with  movable  joints  so  as  to  be  closed  for  transportation. 

494. — If  a  covered  kitchen  is  desired,  either  a  trench  similar 
to  Fig.  2,  can  be  dug,  or  one  above  ground  can  be  built  with 
stones  and  sods  and  a  tent  placed  over  it,  or  a  cover  con- 
structed. 

495. — To  bake  bread,  when  none  of  the  portable  ovens  of  the 
Commissary  Department  are  carried,  improvised  ovens  must  be 
constructed.  The  simplest  method  is  to  take  a  barrel  with  one 
head  out  (one  with  iron  hoops  best),  lay  it  on  its  side  in  a  hollow 
in  the  ground  and  then  plaster  over  with  wet  clay  6  to  8  in. 
thick,  then  with  a  layer  of  dry  earth  equally  thick,  leaving  an 
opening  of  3  or  4  in.  at  the  top  of  the  closed  end  for  a  flue.  The 
staves  are  then  burned  out  by  a  hot  fire  which  also  bakes  the 
clay  covering,  forming  an  arched  oven.  To  bake,  after  heating, 
the  front  and  flues  are  closed.  Or  a  pit  may  be  dug  from  6  to  12 
in.  deep  and  4  by  5  ft.  for  the  hearth,  over  this  form  an  arch  with 
a  hurdle  or  any  other  material  available  (Fig.  7),  with  a  chim- 
ney at  one  end  and  a  door  at  the  other.  Then  plaster  and  cover 
the  arch  as  in  the  barrel  oven  and  bake  the  clay  covering. 

496. — An  oven  may  be  excavated  in  a  clay  bank  (Fig.  6)  and 
used  at  once. 

497. — The  Buzzacott  Army  Field  Oven  (Fig.  8)  which  is  an. arti- 
cle of  issue  by  the  Commissary  Department,  is  a  complete  camp 
cooking  outfit  consisting  of  oven,  baking  and  frying  pans,  etc. 
All  are  securely  packed  togther  and  can  be  conveniently  carried 
in  the  feed  box  of  an  army  wagon  or  on  a  pack  animal.  To  use 
it,  a  bed  of  live  coals  is  first  obtained,  then  the  oven  after  being 
heated  is  placed  on  rests  over  a  bed  of  the  coals,  and  a  layer  of 
sand  sprinkled  evenly  over  the  bottom  of  the  oven  to  prevent 
burning  out.  In  this  is  placed  the  pans  of  prepared  food  on  suit- 
able rests  and  the  whole  covered  with  a  hood.  On  the  hood  is 
scattered  a  layer  of  live  coals  and  burning  brands.  Broiling, 
frying,  coffee  making,  etc.,  may  be  done  on  top  of  the  oven  by 
using  the  remaining  pans,  rests,  etc.,  at  the  same  time  that  the  in- 
terior is  used  for  baking. 


270  Camping  Expedients. 

498. — Drainage.  The  'camp  being  located,  a  system  of  sur- 
face drainage  should  be  carefully  traced  and  constructed.  As 
soon  as  a  tent  is  pitched  it  should  be  surrounded  by  a  shallow 
ditch  outside,  emptying  into  a  company  ditch.  The  proper 
•method  of  doing  this  is  to  have  the  inner  edge  of  the  ditch  come 
just  inside  of  the  skirt  wall  of  the  tent  to  catch  the  water  run- 
ning down  the  side  of  the  tent  and  to  drain  the  interior. 

The  picket  should  be  inside  ot  the  ditch.  (Fig.  9.)  To  bank 
earth  up  against  the  tent  soon  rots  the  bottom  of  the  wall. 

499. — Beds.  The  ground  being  generally  too  damp  to  lie  upon 
directly,  all  should  sleep  upon  some  dry  material  as  straw,  leaves, 
or  preferably  a  low  platform  constructed  of  small  branches  and 
poles,  if  available.     (Pig.  10.) 

If  required  to  sleep  upon  the  ground,  one  w411  sleep  more  com- 
fortably if  he  scrapes  out  a  small  hollow  for  his  hips.  Straw, 
hay,  etc.,  for  sleeping  upon  may  be  made  into  mats  with  the 
Malay  Hitch  as  in  Fig  11. 

500. — Windbreaks.  When  troops  bivouac,  some  protection 
from  wind  may  be  obtained  by  building  up  to  the  windward  a 
pile  of  earth,  sods,  etc.  Where  trees  are  available,  by  resting  a 
pole  on  two  forked  sticks,  4  or  5  ft.  high,  against  which  branches, 
thick  end  up,  are  piled  at  an  angle  of  45°  on  the  windward  side. 
(Fig.  12.)  Hurdles  similarly  placed,  supported  and  covered 
(Fig.  13),  canvas  or  blankets  secured  as  in  Fig.  14,  straw  or  hay 
clamped  between  poles  as  in  Fig.  15,  may  be  used. 

By  throwing  up  either  a  half  or  whole  circle  of  earth  18  ft.  in 
diameter,  from  a  ditch  on  the  outside,  some  protection  may  be  ob- 
tained. On  the  bank  so  formed  additional  wind-breaks  may  be 
placed  or  a  covering  extended  over  it  all  may  be  made.  (PI. 
60,  Figs.  1  and  2.) 

501. — In  cases  of  prolonged  occupation,  if  tents  are  not  avail- 
able, the  troops  should  build  shelter  of  some  kind. 

Huts  may  be  built  of  timber,  logs,  brushwood,  adobe,  etc.,  in 
connection  with  straw,  bark,  sods  and  similar  materials. 

All  huts  should,  if  possible,  have  their  floors  raised  above  the 
ground  to  allow  free  circulation  of  air  underneath.  (Fig.  3.) 
Only  in  very  dry  soil  and  when  not  to  be  occupied  long  is  it  allow- 
able to  sink  them,  if  avoidable.  Space  between  huts  in  the  same 
row  should  equal  the  height  of  walls,  and  passage  in  rear  equal 
the  height  of  ridge.    Hut  sites  should  be  well  pounded. 


PLATE  60. 


Camping  Expedients.  273 

Huts  are  ordinarily  constructed  to  contain  a  small  number  of 
men,  but  the  sizes  and  details  of  construction  will  depend  greatly 
upon  the  site  and  materials  available. 

A  very  fair  minimum  allowance  per  man  of  bed  space  is  about 
2.5  ft.  X  7  ft.,  with  a  passage  at  foot  from  2  to  4  ft. 

Thus,  the  plan  for  8  men  may  be  taken  at  10  ft.  x  18  ft., 
arranged  as  in  Fig.  4.  For  12  men,  15  ft.  x  18  ft.  For  16  men,  20 
ft.  x  18  ft.    For  20  men,  25  ft.  x  18  ft. 

For  calculating  the  accommodation  at  the  above  rates,  allow 
one  man  per  pace  of  length  for  a  single  row  of  beds  and  2  men  per 
pace  of  length  for  a  double  row  of  beds. 

502. — Major  Smart,  Medical  Department,  reconmiends  as  best 
a  modification  of  the  Army  of  the  Potomac  hut,  of  rectangular 
plan  (Fig.  5),  7  ft.  x  13  ft.,  height  to  eaves  6  ft.,  to  ridge  10  ft.;  door 
in  middle  of  one  long  side,  chimney  opposite  door  on  outside  of 
wall ;  on  each  side  of  doorway  a  double  bunk.  This  hut  to  accom- 
modate 4  men. 

If  logs  are  used,  the  ends  are  trimmed  with  an  axe  where  they 
lap  at  the  corners,  so  they  will  lie  one  upon  the  other  throughout 
their  length. 

503. — ^If  made  of  small  timber,  some  style,  as  in  Fig.  6,  with 
thatched  roof,  might  be  used. 

If,  for  any  reason,  it  is  not  desirable  to  build  huts  as  above, 
forms  may  be  used  as  shown  in  Fig.  7,  or  hurdles,  as  in  Fig.  8. 

504. — Sentry  boxes  may  be  made  as  in  Fig.  9,  the  side  cover- 
ing consisting  of  watling  described  in  Chap.  IX.  and  the  roof 
thatched. 


INDEX. 


Par. 

Abatis,  consists  of,  how  made. . .  50 
in    shallow     ditch,    of     small 

branches^in  front  of  glacis  ...  51 

how  destroyed 450 

Advanced  Post,  rear  of 204 

Anchors,  number  of,  scarcity  of.  343 

substitutes  for 344 

use  of 342 

weights  of,  names  of  parts  of..  341 

Angle,  equal   to   a   given   angle, 

method  of  laying  out 22 

right^  method  of  laying  out. . .  18 

rd-entrant,  salient,  shoulder..  82 

Approaches,  in  siege  operations 

constructed  by  infantry 154 

Area,  of  rectangle,  of  trapezoid, 

of  triangle,  method  of  finding.  25 

Artillery,   in  defense  of  village, 

where  placed 215 

in  woods 179 

projectiles    9 

to  be  placed  outside  of  works 

87,  151 

Axe,  use  of...       44 

Balks,  bay,  etc.,  defined 248 

Ballast,  for  R.  R.,  object  of 377 

Bank,  Gun,  definition  of,  rela- 
tive advantages  of,  aud  embra- 
sures           70 

dimensions  of,  where  placed..  102 

space  required  for 100 

Barricade,  use  and  construction 

of .'...  fil 

for  doors  of  baildings 195 

Batteries,  telegraph,  how  carried  418 

Bay,  length  of,  how  found 317 

Beds,  camp 499 


Far. 

Berni,  definition  of,  etc 65,  99 

advantages  and  disadvantages 

of 78 

Binding,  fascines 117 

Bisecting:  an  angle,  method  of. . .  20 
Blocks,  description  of,  etc.,  run- 
ning   228 

Blockhouse,  use   and    construc- 
tion of      144 

in  isolated  places 145 

Boat,  buoyancy  of  how  found 316 

Box  or  barrel,  to  sling 223 

ponton,  construction  of 323 

Brackets,  telegraph 410 

Breaking  loads  of  ropes 218 

Breaks  in  telegraph  lines 419 

Bridge,  anchored  to  hawser   ....  343 

beams,  of  iron,  how  destroyed  439 
connection  of  with  shore,  how 

made 350 

computing  strength  of 255 

double  lock 275 

expedients 278 

floating,  description  of ....  306 

flying,  description  of 309 

forming,    by    successive    pon- 
tons   346 

forming,  by  parts 347 

forming,  by  rafts 348 

forming,  by  conversion 349 

masonry,  how  destroyed 443 

maximum  load  for 247 

name   of,  how  derived 248,  310 

Paine's 260 

pile 269 

protection  of,  from  floating  ob- 
jects   352 


Iiri<lj;:e,  coiitiiiiK'tl. 

railroad,  repair  of 405 

requirements  of 244 

short,  how  anchored 343 

single  lock ..    ...  274 

skiffle  sling 2(<) 

spar  railroad 245 

suspension     2s()-6 

suspension,  how  destroyed...  Ill 

swing o51 

trail 308 

treble  sling , . .  277 

twenty-five  feet  or  less 258-i) 

twenty-five  feet  or  over. 26 1,  271,  276 

ISroadskle     village,    how    de- 
fended    213 

IJrush  huts 503 

sentry  boxes 504 

Brushwood,  bundles  of,  vai  ic  tit  s 

and  sizes 115 

rate  and  method  of  clearing.. .  46 

roads 371 

Building:,    defense   of,    how  re- 
garded, first  line,  how  far  dis- 
tant   191 

doors  of,  how  barricaded 195 

flank  defense  of 199 

how  used  for  defense 189 

loopholing  of 194 

materials  used  in  defense  of  . .  200 

precautions  in  defense  of. 198 

removal  of   .      48,445 

requisite  of,  for  defense 190 

steps  in  preparing  for  defense  193 

windows  of,  how  barricaded..  197 

Buoyancy  of  casks,    how  deter- 
mined   325 

liuzzacott  oven,  description  of..  497 

Cable,  charge  of  explosive  to  cut.  441 

swinging,  length  of 309 

Camp  beds 499 

Camps,  drainage  of 498 

dry  and  healthy  sites  for..  ..457,  459 

selection  of 455,  456,  462 

UBhealthy  sites  for 458,460 

windbreaks  for 500 

Canister,  description  of ll 

Canvas  ponton,  U.  S 319 


Par. 

Canvas  raft,  description  of 303 

Capital  of  field  works 82 

Caponiers,  objections  to 85,  146 

stockade  work  used  for 188 

used  in  flanking  buildings 199 

Capstan,  description  of 212 

Casemate,  use  and  general  form 

of 138 

how    constructed,  floor   siiace 

in i;;n 

Cask,    buoyancy    of,   how   deter- 
mined   325 

Casks,  closed,  piers  of,  construc- 
tion of 330 

open,  piers  of,  construction  of  328 

open,  safe  load  of 329 

Centrifugal  foree  of  train 383 

Charcoal,  uses  of 481 

how  made    482 

Charges,    several    exploded    at 

same  time   429 

Chess  described 218 

Chevaux-de-f  rise 56 

Choker  fascine,  description  and 

use  of 117 

Circular  village,  how  defended  214 

Clarification  of  water 476 

Clay  roads    367 

Command  of  works,  definition 

of 71 

Common     trench     work,      how 

made,  uses  of 156 

Communications,    construction 

of 373,  374 

in  woods 177 

Concentrated  load  on  bridge. . .  253 

Conductor,metallic, for  telegraph  408 

Connecting  wires,  how  done. . .  428 

Corduroy  roads 370 

Counter-scarp,  definition,  etc.. 65,  79 

gal  leries 85 

Cover  for  guns 39 

in  woods,  how  obtained 176 

Crab 240 

Crest,  exterior 67 

interior 66 

military 153 

Crib  piers,  construction  of 268 

ponton,  construction  of 322 


iWDEX. 


•^n 


Par. 

Cross,  in  telegiaj)h  wires 419 

Cross  arms,  telegraph 110 

Crossing:  of  rivers,  selection   of, 

how  determined 289 

Crossing's,  railroad 385 

CroAv's  feet 56 

Cutting:,  how  defended 171,  1T2 

Dead  load  on  bridges 253 

Debris,  removal  of 48 

I>efenders  of  woods,  number  of.     179 

Defense,  of  fences 168 

passive,  with  respect  to  lines 

of  works 149 

Defilade,  definition  of 88 

in  plan , 89 

in  section 90,  91 

with  two  planes 92 

Depth  of  fords       290 

Derrick,  description  of 237 

in  using 240 

Destroying:   railroads,  by  whom 

done 399,  400 

by  whom  ordered 401 

of  telegraph  lines 420 

Detonator 424 

with  fuse 426 

electrical 427 

Dig:g:ing:  wells 470,  471,  472 

Dimensions  of  loop  holes 164 

Disabling:  railroads 398 

Distance  between  two  inaccessi- 
ble points,  method  of  finding..      24 

Distributed  load 253 

Ditch. 65.81,361 

depth  of 96 

method  of  digging 101 

Doors,  how  barricaded 195 

Double  lock  bridge 275 

Drains,  catch  and  covered 361 

Drainag:e  of  camps 498 

of  roads ....     361 

Drinking:  water 465-9 

Driven  wells 473-4 

Driving:  piles 270 

Dynamite,  use  of  with  detonator    429 

Karth.  excess  of  at  salients 97 

in  embankments,  space  occu- 
pied by 96 


Far. 
Karth,  <'ontinued. 

loosening    of   in    the    front   of 

trenches 38 

roads 366 

Earthworks,   calculation  of   di- 
mensions of 95 

Klectrical  fuse  or  detonator. . .   .  427 

Kmbankment,  how  defended. . .  170 

Embarkation,  in  ferrying 301 

Embrasure 69 

used   when,    details   and  con- 
struction of 103 

space  required  for 100 

Eng:ine,  locomotive 389 

Eng:ineering:,     Military,     Field, 

definition  of 1 

Epaulement,  gun 39,  70 

relative  advantage  of,  and  em- 
brasures   70 

Equilateral    triang:le,    method 

of  laying  out .    21 

Escape  in  telegraph  lines 419 

Escarp 65,79 

Expedients,  bridge. 27S 

Exploder,  electrical 428 

Explosives,  kind  generally  used.  421 

table  of  comparative  strength 

of 448 

Extending:  along  zig-zag 155 

working  party 109,  110,  155 

Extension  on  flying  sap,  method 

of 158 

Eye-bars,  how  cut 440 

Eye  splice,  to  make 222 

Faces  of  works 82 

Farms,  principles  of  defense  ap- 
plied to 203 

Fascines,  size,  weight,  and  mak- 
ing of - 117 

Fastening:s,  rail 382 

Faults  in  telegraph  lines 419-20 

Fences,  defense  of 168 

removal  of  when 48 

Ferry,  the  rope 307 

Ferrying:   by  boat,  embarkation, 

and  unloading     301 

by  raft 302 


Index. 


Field  gfunn,  destruction  of. 

range  of 

Field  level,  description  of 
Filters,  portable 

simple 

Filtering  water 

Fire,  as  regards  direction,  trajec- 
tory  

double  tier  of,  for  walls 

sector  of,  discussion  of 

working  parties  exposed  to . . . 

Flank  defense  of  buildings 

Flanks  of  works 

Floor  space  in  casemates 

Floating  piers,  essentials  of 

Flying  bridges,  raft  for 

telegraph  lines 

sap,  description  of 

sap,  method  of  extension  along 
Fords,  how  made  impassable .... 

with  sandy  bottom 

depth  of,  requisite  of 

in  mountainous  country 

level  country 

how  marked,  position  of,  how 
determined 

precautions  in  selecting 

re-examination  of     

where  found 

Foreground,  extent  of  clearing. 
Form,  strap-iron  gabion 

wicker  gabion 

of  roads  

Forming  bridge  by  conversion. 

by  parts 

by  rafts 

by  successive  pontons 

Forts,  how  distinguished 

Fort  Wagner,  parallels  and  ap- 
proaches to  

Fortification,  classes  of 

compared  to  other  military  ex- 
pedients   

object  of 

subdivision  of  field 

Fougasse,  construction,  use,  and 

charge  for  

Fraises,  construction  and  use  of. 


Par. 

447 

13 

26 

483-4 

485 

480-1 


167 
86 
111 
199 
82 
139 
314 
340 
418 
157 
158 
58 
291 
290 
291 
291 

293 
295 
296 
292 

43 
120 
118 
359 
349 
347 
348 
346 

84 

160 
2 


Par. 
Frogs 384 

railroad,  how  destroyed 436 

Fuse 425 

how  used 426 


Gabions,     hoop    or    strap    iron. 

weight  and  making  of 

120 

method  of  carrying             .   .   . 

157 

sheet  iron,  making  of.  . 

191 

wicker,  size,  weight,  and  mak- 

ing of 

118 

making    of  without  a    gabion 

form 

119 

Gates,  desti uction  of 

444 

Gin,  description  of 

239 

using 

'?40 

lashing,  making  of  

227 

Glacis 65,  80 

Gorge  of  works 

82 

Gradient,  limiting  of  roads 

355 

Grain,  removal  of  standing 

47 

Grass,  removal  of  standing 

47 

Gravel  roads                          

368 

Grillage    

493 

Gauge  of  railroads 

380 

Guarding  water  supply 

464 

4?? 

how  detonated 

423 

Gun  epaulements  and  pits 

39 

Gunpowder,  how  ignited 

426 

447 

Gutters 

361 

Hard  Water 477 

Hasty  Demolition,  tables  show- 
ing charges  for 448 

Head  Logs,  use  of 36 

Healthy  Camps 457,  459 

Hedges,  advantages  of,  how   de- 
rived, principles  of 169 

Hedges,  removed,  when 48 

Heights  over  which    tire   may  be 

delivered 13 

Hitches,  knots,  etc 219 

Holdfasts,  description  of 243 

Hoops,  making  of,  for  strap  iron 

gabions 120 

Horse,  power  of  on  grades 356 

Houses,  demolition  of 445 


Index. 


279 


Par. 

Hurdles,    continuous,    construc- 
tion of 123 

size,  weight  and  making  of. . .  122 

Huts,  brush 503 

how  made,  etc 501 

Army     of     Potomac,     (Major 

Smart's) 502 

allowance  of  space  in , . . . .  501 

Ice 297 

thickness  of,  how  increased. . .  299 

thickness  of  for  various  loads.  298 
Infantry  Approaches  in  siege 

operations 154 

Intervals  between  trenches, 34 

method  of  taking   by,  working 

parties 109 

usual  for  working  parties. .  .111,112 

Insulators,  telegraph 412 

Insulated  wire  joints 429 

Iron  plates,  how  cut 438 

Isolated  pits 32 

Joints  for  telegraph  wire  417 

American  twist . 417 

insulation  of 429 

rail 381 

Junctions,  railroad 886 

King:  post  truss 272 

Kitchens 491-2 

covered ,  494 

Knots,  hitches,  etc 219 

Lances,  military,  telegraph 418 

Lashings,  gin 227 

rack 224 

shear 226 

transom 225 

Latrines 487,  490 

Leaks  in  telegraph  line 419 

Level,  field,  description  of 26 

uses  of 27 

Lines,      cutting     of     ditch     and 

trench 101 

Line,    first,     falling     back     past 

houses 192 

parallel  to  given  line,  method 

of  constructing 23 

Lines,  second  and  third  in  woods.  178 


Par. 
Load,    distributed,     dead,      and 

moving 253 

Loading:      horses      in    railroad 

cars 393,  394 

Loading:    wagons    on    railroad 

cars   396 

Log,  cubic  contents  of 254,  335 

buoyancy  of 334 

Logs,  piers  of,  construction  of. . .  338 

Long  splice,  to  make 321 

Loop  holes,  dimensions  of 164 

height  of,  how  influenced 166 

how  made 36 

in  buildings 194 

Loopholing  walls 163 

method  of 164,  165 

Macadam  roads 364 

Machicoulis    gallery,    construc- 
tion of,  use  of  199 

Magazine,  general  plan  of. . .  .141,  142 

large,  small  in  parapet 140 

of  gabions  and  fascines 143 

rifle,  range,  speed,  and  fire  of.  14 

Magneto  exploder 428 

Marking  fords 293 

Materials  for  bridges 287 

for  road  coverings 365 

revetting 114 

used  in  defense  of  buildings. .  200 

Maximum  load  for  bridge 247 

Merlon,  definition  of,   rule  as  to 

minimum  length  of 104 

Metal  ties 379 

Military  engineers,  duties  of..  421 

Military  telegraph  lines 418 

Mines,  land 60 

Moving  or  live  loads 253 

Objects,    floating,  protection    of 

bridge  from 852 

Obstacles,  conditions  governing 

use  of 49 

Office  telegraph,   treatment  of 

when  captured 420 

Ovens 495-6 

Buzzacott     497 

Organizations,  or  parts  of,  used 

as  working  parties 42 

Overhaul  tackle 231 


Ini^kx. 


rar. 

I*aiiie'8  britljjo 260 

Falisatles,  consist  of 54 

I'aliKadiii^,  destruction  of l;>3,  451 

l»airiiig: 118 

I*aii  coupe 102 

Parados,  definition  of (58 

method  of  determining  height 

of 93 

Parallel  to  a  given  line,  method 

of  constructing 23 

Parallels    and   approaches,  Fort 

Wagner  160 

Parapet .63,  67,  81 

Perpendicular  to  a  line  method 

of  erecting  19 

Pickets,  forked 119 

gabion 118 

Piers,  bridge,  how  destroyed. .  .440,443 

Floating  essentials  of 314 

of  casks,  precautions  in  using.     327 
of  open  boats,   precautions  in 

using 315 

of  open  casks,  construction  of.     328 
of  closed  casks,  construction 

of 330,  333 

of  logs,  construction  of 338,  339 

Pile  bridges  269 

driving 270 

Plank  roads 372 

Planks,    when    used    for    revet- 
ments      124 

Plows,  use  of 40 

Ponton  canvas,  U.  S 319 

crib,  construction  of 322 

Ponton,  box,  construction  of 323 

reserve  train ,  U.  S 320 

wagon  body,  construction  of. .     324 

Poles,  telegraph,  how  numbered.     415 

telegraph,  how  guyed,  number 

to   mile,    preparation    of, 

protection  from  lightning, 

raising  of,  size   of,    where 

run 409-411 

Portable  ranip 393 

filters 483-484 

truss 279 

Position,    defensive,     definition 

of,  chief  requisite  of 4 

choice  of 42 


Par. 
Position,  continued. 

strength  of 153 

conditions  to  be  fulfilled 4 

of  ford,  how  determined, 293 

lN)vver  of  horse  on  slopes 356 

exerted  by  man 236 

of  tackle 2S3-5 

Precautions,  additional,    in   de- 
fending buildings   198 

in  fording  295 

Profiles,  angle,  how  determined.       94 
definition    and  nomenclature 

of 65 

normal,  of  field  works 99 

Profiling,  method  of 94 

Pulley,  description  of 228 


Queen  post  truss. 


Rack,    fascine,    description    and 

use  of 

lashing  to  make, 

Kaft,  canvas,  description  of 

for  trail  bridge 

of  skins 

Rafts,    advantages     and     disad- 
vantages of  

for  flying  bridge 

swinging,  for  traffic 

Rail,  fastenings 

form  of . . . .   

joints 

how  cut 

straightening 

Railroad,  bridge 

crossings 

junction 

wye 

turntable  

Railroads,    duties   of   troops   in 

connection  with 

description  of 

destroying  and   disabling,    by 
whom  done 398- 

how  disabled  and  destroyed. 402, 

repair  of 

rolling  stock,  buildings,  etc.o90. 
Ramp,  portable 

Major  Fechet's .. 


117 
224 

303 
308 
304 

305 
340 
351 

382 
380 
381 
435 
407 
245 
385 
386 
387 
388 

375 
377 

-400 
403 
404 
391 
393 
397 


Index. 


281 


Par. 
Ramp,  continued. 

semi-permanent 395 

simple  form  of 392 

Kandins: 122 

Redoubts 84 

Reliefs,  1st,  2nd  and  3rd,  of  work- 
ing   party,    cutting    lines    for 

tasks  of 101 

of  field  work,  definition  of 72 

Reserve  train,  ponton,  U.  S 320 

Revetment,  definition  of 113 

making  and  qualities  of  adobe.  137 

of  brushwood 128 

of  fascines 129 

■   of  gabion 130 

of  hurdle  and  continuous  hur- 
dle   131 

of  pisa 136 

of  plank 124,  132 

of  posts 135 

of  sand  bag 134 

of  sod 126,  133 

of  timber   125,  132 

Ribbands ... 55 

Road  bed 360 

defense  of 173 

matei  ials 365 

Roads,  brushwood 371 

clay 367 

corduroy 370 

desirable  conditions  in 354 

drainage  of  361 

earth 366 

form  of 359 

gravel  368 

knowledge  of 353 

limiting  gradients  of 355 

plank 372 

repair  of 369 

surface  of 362 

width  of 358 

Roadway,  weight  of,   steadiness 

of 313 

width  of  on  bridges 248,  280-6 

Rope,  breaking  loads   of,    weight 

of ..   218 

composition,  size  of,  etc 216 

Rope,  parts  of 219,  230 

rule  for  strength  of 217 


Par, 

Round  timber,  strength  of 255 

Running:  blocks 228 

Sag:  in  telegraph  wire ••••  414 

Salient  village,  how  defended...  212 
Sand  bag:s,  materials,  size  capa- 
city, and  filling 127 

Sap,  flying,  description  of 157 

Saw, teeth   of 44 

use  of 44 

Sector  of  fire,  definition   of  and 

application  to  different  traces.  86 

Selecting:  camps 455-6,  462 

Sentry  boxes 504 

Sewing:,  method  of,    for   gabions 

and  hurdles 118 

Shear  lashing:s , 226 

Shears,   description  of 238 

method  of  using 240 

Shell 9 

charges,  how  exploded 12 

shrapnel 10 

Short  splice,  to  make 220 

Shovelers,  extra,  provided  when  101 

Siding's,  railroad   384 

Sing:le  lock  bridg:e 274 

Sing:le  sling:  bridg:e 276 

Site  for  floating  bridge,  selection 

of 311 

plane  of,  definition 73 

Size  of  teleg:raph  wire. .........  408 

Slewing • 122 

Slope,  banquette 65 

description   of 17 

exterior 65,  77 

interior 65,  75 

superior 65,  76 

Small  pits,  how  made 57 

how  destroyed 453 

Snatch  block 228 

Sods  for  revetments,  cutting   and 

laying 126 

Span,  superstructure,  stringers  or 

balks,  side  rails,  etc 248 

Spans,  25  ft.  or  less 258,  259 

25  ft.  or   over 261,271,276 

Spars,  arrangement  of 257 

Splice,  long 221 

eye 222 


282 


Index. 


Far. 

Splinter-proof  for   trenches 35 

Stockade,  advantages  of,  defini- 
tion of 180 

how  destroyed 434,  451 

kind  of  timber  preferable  for.     186 

loopholes  in 184 

loopholes,  when  cut   in 185 

of  vertical  timbers 182 

of  same,    square    and    round 

timbers   183 

of  horizontal  timber 187 

Stockade,  of  R.  R.    iron,  destroy- 
ed how   434 

when  employed 181 

work  used  for   tambours   and 

caponiers 188 

Stones  in  trenches,  where  placed      34 

Straightening  rails 407 

Streams,  unfordable,  how  passed    294 
velocity  of,  how  determined..     296 

width  of.  how  determined 312 

Strength  of  materials 249 

of  rope ....217,  218 

Sub-drains  361 

Suspension  bridges 280-6 

Switch,  split  and  stub 384 

Table  of  breaking  loads 218 

of  constants  "C" 253 

of  weights  of  materials 256 

showing  amounts  of  revetting 
materials    for     100    linear 

feet  of  revetment 137 

Tackle,   description  of 229 

formula  for  power  of , 235 

power  of 233-4 

to  prevent  twisting 232 

to  round  in,  to  overhaul 231 

Tambour 147 

stockade  work  used  for 188 

used  in  flanking  buildings  ...  199 

Tasks (PI.  14,  16)  111,  112 

laying  out  of 101 

in  constructing  parallels  and 

approaches PI.  22 

responsibility  for  completion 

of 106 

Telegraph  messages 408 

lines,  how  destroyed 420 


Par. 

Telephone,  outpost  cart  for 418 

Telford  roads 363 

Terreplein 74 

Thickness     of    materials    proof 

against  small  arms 15 

Ties,  metal 379 

wood 378 

Timber  Bridge,  how  destroyed    431 

felled,  removal  of 45 

kinds  preferable  for  stockade     186 

round  for  revetments 125 

standing,  removal  of 43,44 

Tools,    carrying    of   by    working 

parties 108 

cutting,    intrenching   used  in 

the  field 41 

taking  of,  by  working  parties..     107 

used  in  felling  timber 44 

Torpedo,  U.  S.  bridge 432 

Torpedoes,  automatic 454 

Trace,  definition  of 64 

selection  of 89 

Transom,  strength  of 250 

Traverse,  definition  of 68 

method  of  determining  height 

of 93 

Tread  banquette 65 

Treble  sling  bridge 277 

Tree  insulator  and  tie 415 

Trees,  cutting  of .44,  45 

how  to  fell  with  explosives 430 

Trench 65 

common,  uses  of,  how  made. .     156 

drainage  of 98 

method  of  digging ,     101 

Trenches,  advantages  and  disad- 
vantages of 38 

disguising  location  of 38 

intervals  in  line  of 34 

kneeling  or  sitting 30 

location  of 33 

loosening  earth  in  front  of 38 

lying 29 

standing 31 

Troops,  weight  of  on  bridge 252 

Trestles,  capped 264 

tie-block    263 

two-legged 265 

three-legged 266 


Par. 
Trestles,  continued. 

four-legged 267 

six-legged 262 

Truss,  king-post 272 

queen-post 273 

portable 279 

Tunnels,  how  destroyed 446 

repair  of 406 

Turntables,  railroad 388 

Unloading  in  ferrying 301 

horses  from  R.  R.  cars.... 393,  394 
wagons  from  cars , 896 

Urinals 488,489 

Velocity  of  streams,   how  deter- 

'       mined.... 296 

Village,    advantages   and    disad- 
vantages of  for  defense 206 

artillery,  where  placed  in  de- 
fense of 215 

broadside,  how  defended 213 

circular,  how  defended 214 

cover    for    supports    and    re- 
serves in 215 

in    defense      of,     precautions 

necessary 205 

defense  of  depends  on 208 

arrangements  for  defense  of.  205 

garrison  of,  how  determined..  211 

objects  in   holding 207 

salient,  how  defended 212 

value  of,  for  defense 205 

arrangement  for    defense    of, 

how  made 210 

Wagon  body  ponton,  construc- 

struction  of 324 

Wagons,  prepared   for   crossing 

on  ice 299 

AValls,  for  double  tiers  of  fire 167 

discussion  of  as  military   ex- 
pedients      161 

loopholing 163-5 

preparation  of  for  defense 162 

removal  of 48 

how  destroyed 442,  451 

Water,  clarification  of 476 

drinking 465-9 

filtering 480-1 


Index.  283 

Par. 
Water,  continued. 

guarding 464 

necessity  of  and  amount    re- 
quired       ...463-4 

Water  tables  on  roads 361 

Watling 118 

Weeds,  removal  of 47 

Weight  of  materials 256 

of  rope 218 

of  troops  on  bridge 252 

Wells,  digging  of 470-2 

driven 473-4 

Width  of  roads 858 

Winch 240 

Windlass,  description  of 241 

Windbreaks  for  camps 500 

Windows  of  buildings,  how  bar- 
ricaded   197 

Wire,  connection  of 428 

entanglements,  high,  low,  how 

made : 52,  53 

entanglements,  how  destroyed  449 
how    stretched,    hanging    of, 

secured  to 414 

how  strung  across  roads 411 

how  strung  across  streams   . . .  415 

telegraph 408 

tie 413 

Withes,  making  and  use  of 117 

Woods,    artillery  in 179 

communications  in 177 

cover    in 176 

lying   beyond  position 175 

number  of  defenders  of 179 

preparation  of  edge  of 174 

2nd  and  3rd  lines  in 178 

Works,  constructed  by  troops  to 

occupy 5 

double  line  of 150 

fixed  types  of  necessary 6 

groups  of,  intermediate,  when 

used 149 

line   of 148 

advantages  and  principles  of.  149 
Works,  field,  conditions  to  be  ful- 
filled   62 

calculation  of  cross  section  of  95 

classification  as  to  trace 83 

defilade  of .  ^. 88,  89,  90,  91,  92 


1>84 


Indkx. 


Par. 
Works,  oontiiiued. 

details  of  construction  of.99,  100,  101 
length   of    crest   for  assumed 

garrison 100 

open,  closed,  and  half  closed, 

definitions,  advantages  and 

disadvantages 8:1 

continuous  line  of,  cremaillere, 

blunted  redan,  redan  with 


J'ar. 
Works,  continued 

curtains,  terraille,  terraille 

and  redan,  trace  of 152 

Working  parties,  extension  of.  109,  110 

organization  of 105 

when  under  fire Ill 

Wye.  R.  R :!87 

Zig-zag,  direction  of,  length  of.       15!) 
extending  along 155 


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